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perl58delta (1)

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perl58delta - what is new for perl v5.8.0

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Perl Programmers Reference Guide PERL58DELTA(1)

NAME
perl58delta - what is new for perl v5.8.0

DESCRIPTION
This document describes differences between the 5.6.0
release and the 5.8.0 release.

Many of the bug fixes in 5.8.0 were already seen in the
5.6.1 maintenance release since the two releases were kept
closely coordinated (while 5.8.0 was still called
5.7.something).

Changes that were integrated into the 5.6.1 release are
marked "[561]". Many of these changes have been further
developed since 5.6.1 was released, those are marked
"[561+]".

You can see the list of changes in the 5.6.1 release (both
from the 5.005_03 release and the 5.6.0 release) by reading
perl561delta.

Highlights In 5.8.0
o Better Unicode support

o New IO Implementation

o New Thread Implementation

o Better Numeric Accuracy

o Safe Signals

o Many New Modules

o More Extensive Regression Testing

Incompatible Changes
Binary Incompatibility
Perl 5.8 is not binary compatible with earlier releases of
Perl.

You have to recompile your XS modules.

(Pure Perl modules should continue to work.)

The major reason for the discontinuity is the new IO
architecture called PerlIO. PerlIO is the default
configuration because without it many new features of Perl
5.8 cannot be used. In other words: you just have to
recompile your modules containing XS code, sorry about that.

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In future releases of Perl, non-PerlIO aware XS modules may
become completely unsupported. This shouldn't be too
difficult for module authors, however: PerlIO has been
designed as a drop-in replacement (at the source code level)
for the stdio interface.

Depending on your platform, there are also other reasons why
we decided to break binary compatibility, please read on.

64-bit platforms and malloc
If your pointers are 64 bits wide, the Perl malloc is no
longer being used because it does not work well with 8-byte
pointers. Also, usually the system mallocs on such
platforms are much better optimized for such large memory
models than the Perl malloc. Some memory-hungry Perl
applications like the PDL don't work well with Perl's
malloc. Finally, other applications than Perl (such as
mod_perl) tend to prefer the system malloc. Such platforms
include Alpha and 64-bit HPPA, MIPS, PPC, and Sparc.

AIX Dynaloading
The AIX dynaloading now uses in AIX releases 4.3 and newer
the native dlopen interface of AIX instead of the old
emulated interface. This change will probably break
backward compatibility with compiled modules. The change
was made to make Perl more compliant with other applications
like mod_perl which are using the AIX native interface.

Attributes for "my" variables now handled at run-time
The "my EXPR : ATTRS" syntax now applies variable attributes
at run-time. (Subroutine and "our" variables still get
attributes applied at compile-time.) See attributes for
additional details. In particular, however, this allows
variable attributes to be useful for "tie" interfaces, which
was a deficiency of earlier releases. Note that the new
semantics doesn't work with the Attribute::Handlers module
(as of version 0.76).

Socket Extension Dynamic in VMS
The Socket extension is now dynamically loaded instead of
being statically built in. This may or may not be a problem
with ancient TCP/IP stacks of VMS: we do not know since we
weren't able to test Perl in such configurations.

IEEE-format Floating Point Default on OpenVMS Alpha
Perl now uses IEEE format (T_FLOAT) as the default internal
floating point format on OpenVMS Alpha, potentially breaking
binary compatibility with external libraries or existing
data. G_FLOAT is still available as a configuration option.
The default on VAX (D_FLOAT) has not changed.

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New Unicode Semantics (no more "use utf8", almost)
Previously in Perl 5.6 to use Unicode one would say "use
utf8" and then the operations (like string concatenation)
were Unicode-aware in that lexical scope.

This was found to be an inconvenient interface, and in Perl
5.8 the Unicode model has completely changed: now the
"Unicodeness" is bound to the data itself, and for most of
the time "use utf8" is not needed at all. The only
remaining use of "use utf8" is when the Perl script itself
has been written in the UTF-8 encoding of Unicode. (UTF-8
has not been made the default since there are many Perl
scripts out there that are using various national eight-bit
character sets, which would be illegal in UTF-8.)

See perluniintro for the explanation of the current model,
and utf8 for the current use of the utf8 pragma.

New Unicode Properties
Unicode scripts are now supported. Scripts are similar to
(and superior to) Unicode blocks. The difference between
scripts and blocks is that scripts are the glyphs used by a
language or a group of languages, while the blocks are more
artificial groupings of (mostly) 256 characters based on the
Unicode numbering.

In general, scripts are more inclusive, but not universally
so. For example, while the script "Latin" includes all the
Latin characters and their various diacritic-adorned
versions, it does not include the various punctuation or
digits (since they are not solely "Latin").

A number of other properties are now supported, including
"\p{L&}", "\p{Any}" "\p{Assigned}", "\p{Unassigned}",
"\p{Blank}" [561] and "\p{SpacePerl}" [561] (along with
their "\P{...}" versions, of course). See perlunicode for
details, and more additions.

The "In" or "Is" prefix to names used with the "\p{...}" and
"\P{...}" are now almost always optional. The only exception
is that a "In" prefix is required to signify a Unicode block
when a block name conflicts with a script name. For example,
"\p{Tibetan}" refers to the script, while "\p{InTibetan}"
refers to the block. When there is no name conflict, you can
omit the "In" from the block name (e.g.
"\p{BraillePatterns}"), but to be safe, it's probably best
to always use the "In").

REF(...) Instead Of SCALAR(...)
A reference to a reference now stringifies as
"REF(0x81485ec)" instead of "SCALAR(0x81485ec)" in order to
be more consistent with the return value of ref().

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pack/unpack D/F recycled
The undocumented pack/unpack template letters D/F have been
recycled for better use: now they stand for long double (if
supported by the platform) and NV (Perl internal floating
point type). (They used to be aliases for d/f, but you
never knew that.)

glob() now returns filenames in alphabetical order
The list of filenames from glob() (or <...>) is now by
default sorted alphabetically to be csh-compliant (which is
what happened before in most Unix platforms). (bsd_glob()
does still sort platform natively, ASCII or EBCDIC, unless
GLOB_ALPHASORT is specified.) [561]

Deprecations
o The semantics of bless(REF, REF) were unclear and until
someone proves it to make some sense, it is forbidden.

o The obsolete chat2 library that should never have been
allowed to escape the laboratory has been
decommissioned.

o Using chdir("") or chdir(undef) instead of explicit
chdir() is doubtful. A failure (think
chdir(some_function()) can lead into unintended chdir()
to the home directory, therefore this behaviour is
deprecated.

o The builtin dump() function has probably outlived most
of its usefulness. The core-dumping functionality will
remain in future available as an explicit call to
"CORE::dump()", but in future releases the behaviour of
an unqualified "dump()" call may change.

o The very dusty examples in the eg/ directory have been
removed. Suggestions for new shiny examples welcome but
the main issue is that the examples need to be
documented, tested and (most importantly) maintained.

o The (bogus) escape sequences \8 and \9 now give an
optional warning ("Unrecognized escape passed through").
There is no need to \-escape any "\w" character.

o The *glob{FILEHANDLE} is deprecated, use *glob{IO}
instead.

o The "package;" syntax ("package" without an argument)
has been deprecated. Its semantics were never that
clear and its implementation even less so. If you have
used that feature to disallow all but fully qualified
variables, "use strict;" instead.

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o The unimplemented POSIX regex features [[.cc.]] and
[[=c=]] are still recognised but now cause fatal errors.
The previous behaviour of ignoring them by default and
warning if requested was unacceptable since it, in a
way, falsely promised that the features could be used.

o In future releases, non-PerlIO aware XS modules may
become completely unsupported. Since PerlIO is a drop-
in replacement for stdio at the source code level, this
shouldn't be that drastic a change.

o Previous versions of perl and some readings of some
sections of Camel III implied that the ":raw"
"discipline" was the inverse of ":crlf". Turning off
"clrfness" is no longer enough to make a stream truly
binary. So the PerlIO ":raw" layer (or "discipline", to
use the Camel book's older terminology) is now formally
defined as being equivalent to binmode(FH) - which is in
turn defined as doing whatever is necessary to pass each
byte as-is without any translation. In particular
binmode(FH) - and hence ":raw" - will now turn off both
CRLF and UTF-8 translation and remove other layers (e.g.
:encoding()) which would modify byte stream.

o The current user-visible implementation of pseudo-hashes
(the weird use of the first array element) is deprecated
starting from Perl 5.8.0 and will be removed in Perl
5.10.0, and the feature will be implemented differently.
Not only is the current interface rather ugly, but the
current implementation slows down normal array and hash
use quite noticeably. The "fields" pragma interface will
remain available. The restricted hashes interface is
expected to be the replacement interface (see
Hash::Util). If your existing programs depends on the
underlying implementation, consider using
Class::PseudoHash from CPAN.

o The syntaxes "@a->[...]" and "%h->{...}" have now been
deprecated.

o After years of trying, suidperl is considered to be too
complex to ever be considered truly secure. The
suidperl functionality is likely to be removed in a
future release.

o The 5.005 threads model (module "Thread") is deprecated
and expected to be removed in Perl 5.10. Multithreaded
code should be migrated to the new ithreads model (see
threads, threads::shared and perlthrtut).

o The long deprecated uppercase aliases for the string
comparison operators (EQ, NE, LT, LE, GE, GT) have now

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been removed.

o The tr///C and tr///U features have been removed and
will not return; the interface was a mistake. Sorry
about that. For similar functionality, see pack('U0',
...) and pack('C0', ...). [561]

o Earlier Perls treated "sub foo (@bar)" as equivalent to
"sub foo (@)". The prototypes are now checked better at
compile-time for invalid syntax. An optional warning is
generated ("Illegal character in prototype...") but
this may be upgraded to a fatal error in a future
release.

o The "exec LIST" and "system LIST" operations now produce
warnings on tainted data and in some future release they
will produce fatal errors.

o The existing behaviour when localising tied arrays and
hashes is wrong, and will be changed in a future
release, so do not rely on the existing behaviour. See
"Localising Tied Arrays and Hashes Is Broken".

Core Enhancements
Unicode Overhaul
Unicode in general should be now much more usable than in
Perl 5.6.0 (or even in 5.6.1). Unicode can be used in hash
keys, Unicode in regular expressions should work now,
Unicode in tr/// should work now, Unicode in I/O should work
now. See perluniintro for introduction and perlunicode for
details.

o The Unicode Character Database coming with Perl has been
upgraded to Unicode 3.2.0. For more information, see
http://www.unicode.org/ . [561+] (5.6.1 has UCD 3.0.1.)

o For developers interested in enhancing Perl's Unicode
capabilities: almost all the UCD files are included with
the Perl distribution in the lib/unicore subdirectory.
The most notable omission, for space considerations, is
the Unihan database.

o The properties \p{Blank} and \p{SpacePerl} have been
added. "Blank" is like C isblank(), that is, it contains
only "horizontal whitespace" (the space character is,
the newline isn't), and the "SpacePerl" is the Unicode
equivalent of "\s" (\p{Space} isn't, since that includes
the vertical tabulator character, whereas "\s" doesn't.)

See "New Unicode Properties" earlier in this document
for additional information on changes with Unicode
properties.

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PerlIO is Now The Default
o IO is now by default done via PerlIO rather than
system's "stdio". PerlIO allows "layers" to be "pushed"
onto a file handle to alter the handle's behaviour.
Layers can be specified at open time via 3-arg form of
open:

open($fh,'>:crlf :utf8', $path) || ...

or on already opened handles via extended "binmode":

binmode($fh,':encoding(iso-8859-7)');

The built-in layers are: unix (low level read/write),
stdio (as in previous Perls), perlio (re-implementation
of stdio buffering in a portable manner), crlf (does
CRLF <=> "\n" translation as on Win32, but available on
any platform). A mmap layer may be available if
platform supports it (mostly Unixes).

Layers to be applied by default may be specified via the
'open' pragma.

See "Installation and Configuration Improvements" for
the effects of PerlIO on your architecture name.

o If your platform supports fork(), you can use the list
form of "open" for pipes. For example:

open KID_PS, "-|", "ps", "aux" or die $!;

forks the ps(1) command (without spawning a shell, as
there are more than three arguments to open()), and
reads its standard output via the "KID_PS" filehandle.
See perlipc.

o File handles can be marked as accepting Perl's internal
encoding of Unicode (UTF-8 or UTF-EBCDIC depending on
platform) by a pseudo layer ":utf8" :

open($fh,">:utf8","Uni.txt");

Note for EBCDIC users: the pseudo layer ":utf8" is
erroneously named for you since it's not UTF-8 what you
will be getting but instead UTF-EBCDIC. See
perlunicode, utf8, and
http://www.unicode.org/unicode/reports/tr16/ for more
information. In future releases this naming may change.
See perluniintro for more information about UTF-8.

o If your environment variables (LC_ALL, LC_CTYPE, LANG)
look like you want to use UTF-8 (any of the variables

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match "/utf-?8/i"), your STDIN, STDOUT, STDERR handles
and the default open layer (see open) are marked as
UTF-8. (This feature, like other new features that
combine Unicode and I/O, work only if you are using
PerlIO, but that's the default.)

Note that after this Perl really does assume that
everything is UTF-8: for example if some input handle is
not, Perl will probably very soon complain about the
input data like this "Malformed UTF-8 ..." since any old
eight-bit data is not legal UTF-8.

Note for code authors: if you want to enable your users
to use UTF-8 as their default encoding but in your code
still have eight-bit I/O streams (such as images or zip
files), you need to explicitly open() or binmode() with
":bytes" (see "open" in perlfunc and "binmode" in
perlfunc), or you can just use "binmode(FH)" (nice for
pre-5.8.0 backward compatibility).

o File handles can translate character encodings from/to
Perl's internal Unicode form on read/write via the
":encoding()" layer.

o File handles can be opened to "in memory" files held in
Perl scalars via:

open($fh,'>', \$variable) || ...

o Anonymous temporary files are available without need to
'use FileHandle' or other module via

open($fh,"+>", undef) || ...

That is a literal undef, not an undefined value.

ithreads
The new interpreter threads ("ithreads" for short)
implementation of multithreading, by Arthur Bergman,
replaces the old "5.005 threads" implementation. In the
ithreads model any data sharing between threads must be
explicit, as opposed to the model where data sharing was
implicit. See threads and threads::shared, and perlthrtut.

As a part of the ithreads implementation Perl will also use
any necessary and detectable reentrant libc interfaces.

Restricted Hashes
A restricted hash is restricted to a certain set of keys, no
keys outside the set can be added. Also individual keys can
be restricted so that the key cannot be deleted and the
value cannot be changed. No new syntax is involved: the

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Hash::Util module is the interface.

Safe Signals
Perl used to be fragile in that signals arriving at
inopportune moments could corrupt Perl's internal state.
Now Perl postpones handling of signals until it's safe
(between opcodes).

This change may have surprising side effects because signals
no longer interrupt Perl instantly. Perl will now first
finish whatever it was doing, like finishing an internal
operation (like sort()) or an external operation (like an
I/O operation), and only then look at any arrived signals
(and before starting the next operation). No more corrupt
internal state since the current operation is always
finished first, but the signal may take more time to get
heard. Note that breaking out from potentially blocking
operations should still work, though.

Understanding of Numbers
In general a lot of fixing has happened in the area of
Perl's understanding of numbers, both integer and floating
point. Since in many systems the standard number parsing
functions like "strtoul()" and "atof()" seem to have bugs,
Perl tries to work around their deficiencies. This results
hopefully in more accurate numbers.

Perl now tries internally to use integer values in numeric
conversions and basic arithmetics (+ - * /) if the arguments
are integers, and tries also to keep the results stored
internally as integers. This change leads to often slightly
faster and always less lossy arithmetics. (Previously Perl
always preferred floating point numbers in its math.)

Arrays now always interpolate into double-quoted strings [561]

In double-quoted strings, arrays now interpolate, no matter
what. The behavior in earlier versions of perl 5 was that
arrays would interpolate into strings if the array had been
mentioned before the string was compiled, and otherwise Perl
would raise a fatal compile-time error. In versions 5.000
through 5.003, the error was

Literal @example now requires backslash

In versions 5.004_01 through 5.6.0, the error was

In string, @example now must be written as \@example

The idea here was to get people into the habit of writing
"fred\@example.com" when they wanted a literal "@" sign,
just as they have always written "Give me back my \$5" when

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they wanted a literal "$" sign.

Starting with 5.6.1, when Perl now sees an "@" sign in a
double-quoted string, it always attempts to interpolate an
array, regardless of whether or not the array has been used
or declared already. The fatal error has been downgraded to
an optional warning:

Possible unintended interpolation of @example in string

This warns you that "fred@example.com" is going to turn into
"fred.com" if you don't backslash the "@". See
http://perl.plover.com/at-error.html for more details about
the history here.

Miscellaneous Changes
o AUTOLOAD is now lvaluable, meaning that you can add the
:lvalue attribute to AUTOLOAD subroutines and you can
assign to the AUTOLOAD return value.

o The $Config{byteorder} (and corresponding BYTEORDER in
config.h) was previously wrong in platforms if
sizeof(long) was 4, but sizeof(IV) was 8. The byteorder
was only sizeof(long) bytes long (1234 or 4321), but now
it is correctly sizeof(IV) bytes long, (12345678 or
87654321). (This problem didn't affect Windows
platforms.)

Also, $Config{byteorder} is now computed
dynamically--this is more robust with "fat binaries"
where an executable image contains binaries for more
than one binary platform, and when cross-compiling.

o "perl -d:Module=arg,arg,arg" now works (previously one
couldn't pass in multiple arguments.)

o "do" followed by a bareword now ensures that this
bareword isn't a keyword (to avoid a bug where "do
q(foo.pl)" tried to call a subroutine called "q"). This
means that for example instead of "do format()" you must
write "do &format()".

o The builtin dump() now gives an optional warning "dump()
better written as CORE::dump()", meaning that by default
"dump(...)" is resolved as the builtin dump() which
dumps core and aborts, not as (possibly) user-defined
"sub dump". To call the latter, qualify the call as
"&dump(...)". (The whole dump() feature is to
considered deprecated, and possibly removed/changed in
future releases.)

o chomp() and chop() are now overridable. Note, however,

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that their prototype (as given by
"prototype("CORE::chomp")" is undefined, because it
cannot be expressed and therefore one cannot really
write replacements to override these builtins.

o END blocks are now run even if you exit/die in a BEGIN
block. Internally, the execution of END blocks is now
controlled by PL_exit_flags & PERL_EXIT_DESTRUCT_END.
This enables the new behaviour for Perl embedders. This
will default in 5.10. See perlembed.

o Formats now support zero-padded decimal fields.

o Although "you shouldn't do that", it was possible to
write code that depends on Perl's hashed key order
(Data::Dumper does this). The new algorithm "One-at-a-
Time" produces a different hashed key order. More
details are in "Performance Enhancements".

o lstat(FILEHANDLE) now gives a warning because the
operation makes no sense. In future releases this may
become a fatal error.

o Spurious syntax errors generated in certain situations,
when glob() caused File::Glob to be loaded for the first
time, have been fixed. [561]

o Lvalue subroutines can now return "undef" in list
context. However, the lvalue subroutine feature still
remains experimental. [561+]

o A lost warning "Can't declare ... dereference in my" has
been restored (Perl had it earlier but it became lost in
later releases.)

o A new special regular expression variable has been
introduced: $^N, which contains the most-recently closed
group (submatch).

o "no Module;" does not produce an error even if Module
does not have an unimport() method. This parallels the
behavior of "use" vis-a-vis "import". [561]

o The numerical comparison operators return "undef" if
either operand is a NaN. Previously the behaviour was
unspecified.

o "our" can now have an experimental optional attribute
"unique" that affects how global variables are shared
among multiple interpreters, see "our" in perlfunc.

o The following builtin functions are now overridable:

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each(), keys(), pop(), push(), shift(), splice(),
unshift(). [561]

o "pack() / unpack()" can now group template letters with
"()" and then apply repetition/count modifiers on the
groups.

o "pack() / unpack()" can now process the Perl internal
numeric types: IVs, UVs, NVs-- and also long doubles, if
supported by the platform. The template letters are
"j", "J", "F", and "D".

o "pack('U0a*', ...)" can now be used to force a string to
UTF-8.

o my __PACKAGE__ $obj now works. [561]

o POSIX::sleep() now returns the number of unslept seconds
(as the POSIX standard says), as opposed to
CORE::sleep() which returns the number of slept seconds.

o printf() and sprintf() now support parameter reordering
using the "%\d+\$" and "*\d+\$" syntaxes. For example

printf "%2\$s %1\$s\n", "foo", "bar";

will print "bar foo\n". This feature helps in writing
internationalised software, and in general when the
order of the parameters can vary.

o The (\&) prototype now works properly. [561]

o prototype(\[$@%&]) is now available to implicitly create
references (useful for example if you want to emulate
the tie() interface).

o A new command-line option, "-t" is available. It is the
little brother of "-T": instead of dying on taint
violations, lexical warnings are given. This is only
meant as a temporary debugging aid while securing the
code of old legacy applications. This is not a
substitute for -T.

o In other taint news, the "exec LIST" and "system LIST"
have now been considered too risky (think "exec @ARGV":
it can start any program with any arguments), and now
the said forms cause a warning under lexical warnings.
You should carefully launder the arguments to guarantee
their validity. In future releases of Perl the forms
will become fatal errors so consider starting laundering
now.

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o Tied hash interfaces are now required to have the EXISTS
and DELETE methods (either own or inherited).

o If tr/// is just counting characters, it doesn't attempt
to modify its target.

o untie() will now call an UNTIE() hook if it exists. See
perltie for details. [561]

o utime now supports "utime undef, undef, @files" to
change the file timestamps to the current time.

o The rules for allowing underscores (underbars) in
numeric constants have been relaxed and simplified: now
you can have an underscore simply between digits.

o Rather than relying on C's argv[0] (which may not
contain a full pathname) where possible $^X is now set
by asking the operating system. (eg by reading
/proc/self/exe on Linux, /proc/curproc/file on FreeBSD)

o A new variable, "${^TAINT}", indicates whether taint
mode is enabled.

o You can now override the readline() builtin, and this
overrides also the <FILEHANDLE> angle bracket operator.

o The command-line options -s and -F are now recognized on
the shebang (#!) line.

o Use of the "/c" match modifier without an accompanying
"/g" modifier elicits a new warning: "Use of /c modifier
is meaningless without /g".

Use of "/c" in substitutions, even with "/g", elicits
"Use of /c modifier is meaningless in s///".

Use of "/g" with "split" elicits "Use of /g modifier is
meaningless in split".

o Support for the "CLONE" special subroutine had been
added. With ithreads, when a new thread is created, all
Perl data is cloned, however non-Perl data cannot be
cloned automatically. In "CLONE" you can do whatever
you need to do, like for example handle the cloning of
non-Perl data, if necessary. "CLONE" will be executed
once for every package that has it defined or inherited.
It will be called in the context of the new thread, so
all modifications are made in the new area.

See perlmod

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Modules and Pragmata
New Modules and Pragmata
o "Attribute::Handlers", originally by Damian Conway and
now maintained by Arthur Bergman, allows a class to
define attribute handlers.

package MyPack;
use Attribute::Handlers;
sub Wolf :ATTR(SCALAR) { print "howl!\n" }

# later, in some package using or inheriting from MyPack...

my MyPack $Fluffy : Wolf; # the attribute handler Wolf will be called

Both variables and routines can have attribute handlers.
Handlers can be specific to type (SCALAR, ARRAY, HASH,
or CODE), or specific to the exact compilation phase
(BEGIN, CHECK, INIT, or END). See Attribute::Handlers.

o "B::Concise", by Stephen McCamant, is a new compiler
backend for walking the Perl syntax tree, printing
concise info about ops. The output is highly
customisable. See B::Concise. [561+]

o The new bignum, bigint, and bigrat pragmas, by Tels,
implement transparent bignum support (using the
Math::BigInt, Math::BigFloat, and Math::BigRat
backends).

o "Class::ISA", by Sean Burke, is a module for reporting
the search path for a class's ISA tree. See Class::ISA.

o "Cwd" now has a split personality: if possible, an XS
extension is used, (this will hopefully be faster, more
secure, and more robust) but if not possible, the
familiar Perl implementation is used.

o "Devel::PPPort", originally by Kenneth Albanowski and
now maintained by Paul Marquess, has been added. It is
primarily used by "h2xs" to enhance portability of XS
modules between different versions of Perl. See
Devel::PPPort.

o "Digest", frontend module for calculating digests
(checksums), from Gisle Aas, has been added. See
Digest.

o "Digest::MD5" for calculating MD5 digests (checksums) as
defined in RFC 1321, from Gisle Aas, has been added.
See Digest::MD5.

use Digest::MD5 'md5_hex';

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$digest = md5_hex("Thirsty Camel");

print $digest, "\n"; # 01d19d9d2045e005c3f1b80e8b164de1

NOTE: the "MD5" backward compatibility module is
deliberately not included since its further use is
discouraged.

See also PerlIO::via::QuotedPrint.

o "NEXT", by Damian Conway, is a pseudo-class for method
redispatch. See NEXT.

o "open" is a new pragma for setting the default I/O
layers for open().

o "PerlIO::scalar", by Nick Ing-Simmons, provides the
implementation of IO to "in memory" Perl scalars as
discussed above. It also serves as an example of a

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loadable PerlIO layer. Other future possibilities
include PerlIO::Array and PerlIO::Code. See
PerlIO::scalar.

o "PerlIO::via", by Nick Ing-Simmons, acts as a PerlIO
layer and wraps PerlIO layer functionality provided by a
class (typically implemented in Perl code).

o "PerlIO::via::QuotedPrint", by Elizabeth Mattijsen, is
an example of a "PerlIO::via" class:

use PerlIO::via::QuotedPrint;
open($fh,">:via(QuotedPrint)",$path);

This will automatically convert everything output to $fh
to Quoted-Printable. See PerlIO::via and
PerlIO::via::QuotedPrint.

o "Pod::ParseLink", by Russ Allbery, has been added, to
parse L<> links in pods as described in the new
perlpodspec.

o "Pod::Text::Overstrike", by Joe Smith, has been added.
It converts POD data to formatted overstrike text. See
Pod::Text::Overstrike. [561+]

o "Scalar::Util" is a selection of general-utility scalar
subroutines, such as blessed(), reftype(), and
tainted(). See Scalar::Util.

o "sort" is a new pragma for controlling the behaviour of
sort().

o "Storable" gives persistence to Perl data structures by
allowing the storage and retrieval of Perl data to and
from files in a fast and compact binary format. Because
in effect Storable does serialisation of Perl data
structures, with it you can also clone deep,
hierarchical datastructures. Storable was originally
created by Raphael Manfredi, but it is now maintained by
Abhijit Menon-Sen. Storable has been enhanced to
understand the two new hash features, Unicode keys and
restricted hashes. See Storable.

o "Switch", by Damian Conway, has been added. Just by
saying

use Switch;

you have "switch" and "case" available in Perl.

use Switch;

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switch ($val) {

case 1 { print "number 1" }
case "a" { print "string a" }
case [1..10,42] { print "number in list" }
case (@array) { print "number in list" }
case /\w+/ { print "pattern" }
case qr/\w+/ { print "pattern" }
case (%hash) { print "entry in hash" }
case (\%hash) { print "entry in hash" }
case (\&sub) { print "arg to subroutine" }
else { print "previous case not true" }
}

See Switch.

o "Test::More", by Michael Schwern, is yet another
framework for writing test scripts, more extensive than
Test::Simple. See Test::More.

o "Test::Simple", by Michael Schwern, has basic utilities
for writing tests. See Test::Simple.

o "Text::Balanced", by Damian Conway, has been added, for
extracting delimited text sequences from strings.

use Text::Balanced 'extract_delimited';

($a, $b) = extract_delimited("'never say never', he never said", "'", '');

$a will be "'never say never'", $b will be ', he never
said'.

In addition to extract_delimited(), there are also
extract_bracketed(), extract_quotelike(),
extract_codeblock(), extract_variable(),
extract_tagged(), extract_multiple(),
gen_delimited_pat(), and gen_extract_tagged(). With
these, you can implement rather advanced parsing
algorithms. See Text::Balanced.

o "threads", by Arthur Bergman, is an interface to
interpreter threads. Interpreter threads (ithreads) is
the new thread model introduced in Perl 5.6 but only
available as an internal interface for extension writers
(and for Win32 Perl for "fork()" emulation). See
threads, threads::shared, and perlthrtut.

o "threads::shared", by Arthur Bergman, allows data
sharing for interpreter threads. See threads::shared.

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o "Tie::File", by Mark-Jason Dominus, associates a Perl
array with the lines of a file. See Tie::File.

o "Tie::Memoize", by Ilya Zakharevich, provides on-demand
loaded hashes. See Tie::Memoize.

o "Tie::RefHash::Nestable", by Edward Avis, allows storing
hash references (unlike the standard Tie::RefHash) The
module is contained within Tie::RefHash. See
Tie::RefHash.

o "Time::HiRes", by Douglas E. Wegscheid, provides high
resolution timing (ualarm, usleep, and gettimeofday).
See Time::HiRes.

o "Unicode::UCD" offers a querying interface to the
Unicode Character Database. See Unicode::UCD.

o "Unicode::Collate", by SADAHIRO Tomoyuki, implements the
UCA (Unicode Collation Algorithm) for sorting Unicode
strings. See Unicode::Collate.

o "Unicode::Normalize", by SADAHIRO Tomoyuki, implements
the various Unicode normalization forms. See
Unicode::Normalize.

o "XS::APItest", by Tim Jenness, is a test extension that
exercises XS APIs. Currently only "printf()" is tested:
how to output various basic data types from XS.

o "XS::Typemap", by Tim Jenness, is a test extension that
exercises XS typemaps. Nothing gets installed, but the
code is worth studying for extension writers.

Updated And Improved Modules and Pragmata
o The following independently supported modules have been
updated to the newest versions from CPAN: CGI, CPAN,
DB_File, File::Spec, File::Temp, Getopt::Long,
Math::BigFloat, Math::BigInt, the podlators bundle
(Pod::Man, Pod::Text), Pod::LaTeX [561+], Pod::Parser,
Storable, Term::ANSIColor, Test, Text-Tabs+Wrap.

o attributes::reftype() now works on tied arguments.

o AutoLoader can now be disabled with "no AutoLoader;".

o B::Deparse has been significantly enhanced by Robin
Houston. It can now deparse almost all of the standard
test suite (so that the tests still succeed). There is
a make target "test.deparse" for trying this out.

o Carp now has better interface documentation, and the

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@CARP_NOT interface has been added to get optional
control over where errors are reported independently of
@ISA, by Ben Tilly.

o Class::Struct can now define the classes in compile
time.

o Class::Struct now assigns the array/hash element if the
accessor is called with an array/hash element as the
sole argument.

o The return value of Cwd::fastcwd() is now tainted.

o Data::Dumper now has an option to sort hashes.

o Data::Dumper now has an option to dump code references
using B::Deparse.

o DB_File now supports newer Berkeley DB versions, among
other improvements.

o Devel::Peek now has an interface for the Perl memory
statistics (this works only if you are using perl's
malloc, and if you have compiled with debugging).

o The English module can now be used without the infamous
performance hit by saying

use English '-no_match_vars';

(Assuming, of course, that you don't need the
troublesome variables "$`", $&, or "$'".) Also,
introduced @LAST_MATCH_START and @LAST_MATCH_END English
aliases for "@-" and "@+".

o ExtUtils::MakeMaker has been significantly cleaned up
and fixed. The enhanced version has also been
backported to earlier releases of Perl and submitted to
CPAN so that the earlier releases can enjoy the fixes.

o The arguments of WriteMakefile() in Makefile.PL are now
checked for sanity much more carefully than before.
This may cause new warnings when modules are being
installed. See ExtUtils::MakeMaker for more details.

o ExtUtils::MakeMaker now uses File::Spec internally,
which hopefully leads to better portability.

o Fcntl, Socket, and Sys::Syslog have been rewritten by
Nicholas Clark to use the new-style constant dispatch
section (see ExtUtils::Constant). This means that they
will be more robust and hopefully faster.

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o File::Find now chdir()s correctly when chasing symbolic
links. [561]

o File::Find now has pre- and post-processing callbacks.
It also correctly changes directories when chasing
symbolic links. Callbacks (naughtily) exiting with
"next;" instead of "return;" now work.

o File::Find is now (again) reentrant. It also has been
made more portable.

o The warnings issued by File::Find now belong to their
own category. You can enable/disable them with "use/no
warnings 'File::Find';".

o File::Glob::glob() has been renamed to
File::Glob::bsd_glob() because the name clashes with the
builtin glob(). The older name is still available for
compatibility, but is deprecated. [561]

o File::Glob now supports "GLOB_LIMIT" constant to limit
the size of the returned list of filenames.

o IPC::Open3 now allows the use of numeric file
descriptors.

o IO::Socket now has an atmark() method, which returns
true if the socket is positioned at the out-of-band
mark. The method is also exportable as a sockatmark()
function.

o IO::Socket::INET failed to open the specified port if
the service name was not known. It now correctly uses
the supplied port number as is. [561]

o IO::Socket::INET has support for the ReusePort option
(if your platform supports it). The Reuse option now
has an alias, ReuseAddr. For clarity, you may want to
prefer ReuseAddr.

o IO::Socket::INET now supports a value of zero for
"LocalPort" (usually meaning that the operating system
will make one up.)

o 'use lib' now works identically to @INC. Removing
directories with 'no lib' now works.

o Math::BigFloat and Math::BigInt have undergone a full
rewrite by Tels. They are now magnitudes faster, and
they support various bignum libraries such as GMP and
PARI as their backends.

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o Math::Complex handles inf, NaN etc., better.

o Net::Ping has been considerably enhanced by Rob Brown:
multihoming is now supported, Win32 functionality is
better, there is now time measuring functionality
(optionally high-resolution using Time::HiRes), and
there is now "external" protocol which uses
Net::Ping::External module which runs your external ping
utility and parses the output. A version of
Net::Ping::External is available in CPAN.

Note that some of the Net::Ping tests are disabled when
running under the Perl distribution since one cannot
assume one or more of the following: enabled echo port
at localhost, full Internet connectivity, or sympathetic
firewalls. You can set the environment variable
PERL_TEST_Net_Ping to "1" (one) before running the Perl
test suite to enable all the Net::Ping tests.

o POSIX::sigaction() is now much more flexible and robust.
You can now install coderef handlers, 'DEFAULT', and
'IGNORE' handlers, installing new handlers was not
atomic.

o In Safe, %INC is now localised in a Safe compartment so
that use/require work.

o In SDBM_File on dosish platforms, some keys went missing
because of lack of support for files with "holes". A
workaround for the problem has been added.

o In Search::Dict one can now have a pre-processing hook
for the lines being searched.

o The Shell module now has an OO interface.

o In Sys::Syslog there is now a failover mechanism that
will go through alternative connection mechanisms until
the message is successfully logged.

o The Test module has been significantly enhanced.

o Time::Local::timelocal() does not handle fractional
seconds anymore. The rationale is that neither does
localtime(), and timelocal() and localtime() are
supposed to be inverses of each other.

o The vars pragma now supports declaring fully qualified
variables. (Something that "our()" does not and will
not support.)

o The "utf8::" name space (as in the pragma) provides

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various Perl-callable functions to provide low level
access to Perl's internal Unicode representation. At
the moment only length() has been implemented.

Utility Changes
o Emacs perl mode (emacs/cperl-mode.el) has been updated
to version 4.31.

o emacs/e2ctags.pl is now much faster.

o "enc2xs" is a tool for people adding their own encodings
to the Encode module.

o "h2ph" now supports C trigraphs.

o "h2xs" now produces a template README.

o "h2xs" now uses "Devel::PPPort" for better portability
between different versions of Perl.

o "h2xs" uses the new ExtUtils::Constant module which will
affect newly created extensions that define constants.
Since the new code is more correct (if you have two
constants where the first one is a prefix of the second
one, the first constant never got defined), less lossy
(it uses integers for integer constant, as opposed to
the old code that used floating point numbers even for
integer constants), and slightly faster, you might want
to consider regenerating your extension code (the new
scheme makes regenerating easy). h2xs now also supports
C trigraphs.

o "libnetcfg" has been added to configure libnet.

o "perlbug" is now much more robust. It also sends the
bug report to perl.org, not perl.com.

o "perlcc" has been rewritten and its user interface (that
is, command line) is much more like that of the Unix C
compiler, cc. (The perlbc tools has been removed. Use
"perlcc -B" instead.) Note that perlcc is still
considered very experimental and unsupported. [561]

o "perlivp" is a new Installation Verification Procedure
utility for running any time after installing Perl.

o "piconv" is an implementation of the character
conversion utility "iconv", demonstrating the new Encode
module.

o "pod2html" now allows specifying a cache directory.

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o "pod2html" now produces XHTML 1.0.

o "pod2html" now understands POD written using different
line endings (PC-like CRLF versus Unix-like LF versus
MacClassic-like CR).

o "s2p" has been completely rewritten in Perl. (It is in
fact a full implementation of sed in Perl: you can use
the sed functionality by using the "psed" utility.)

o "xsubpp" now understands POD documentation embedded in
the *.xs files. [561]

o "xsubpp" now supports the OUT keyword.

New Documentation
o perl56delta details the changes between the 5.005
release and the 5.6.0 release.

o perlclib documents the internal replacements for
standard C library functions. (Interesting only for
extension writers and Perl core hackers.) [561+]

o perldebtut is a Perl debugging tutorial. [561+]

o perlebcdic contains considerations for running Perl on
EBCDIC platforms. [561+]

o perlintro is a gentle introduction to Perl.

o perliol documents the internals of PerlIO with layers.

o perlmodstyle is a style guide for writing modules.

o perlnewmod tells about writing and submitting a new
module. [561+]

o perlpacktut is a pack() tutorial.

o perlpod has been rewritten to be clearer and to record
the best practices gathered over the years.

o perlpodspec is a more formal specification of the pod
format, mainly of interest for writers of pod
applications, not to people writing in pod.

o perlretut is a regular expression tutorial. [561+]

o perlrequick is a regular expressions quick-start guide.
Yes, much quicker than perlretut. [561]

o perltodo has been updated.

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o perltootc has been renamed as perltooc (to not to
conflict with perltoot in filesystems restricted to
"8.3" names).

o perluniintro is an introduction to using Unicode in
Perl. (perlunicode is more of a detailed reference and
background information)

o perlutil explains the command line utilities packaged
with the Perl distribution. [561+]

The following platform-specific documents are available
before the installation as README.platform, and after the
installation as perlplatform:

perlaix perlamiga perlapollo perlbeos perlbs2000
perlce perlcygwin perldgux perldos perlepoc perlfreebsd perlhpux
perlhurd perlirix perlmachten perlmacos perlmint perlmpeix
perlnetware perlos2 perlos390 perlplan9 perlqnx perlsolaris
perltru64 perluts perlvmesa perlvms perlvos perlwin32

These documents usually detail one or more of the following
subjects: configuring, building, testing, installing, and
sometimes also using Perl on the said platform.

Eastern Asian Perl users are now welcomed in their own
languages: README.jp (Japanese), README.ko (Korean),
README.cn (simplified Chinese) and README.tw (traditional
Chinese), which are written in normal pod but encoded in
EUC-JP, EUC-KR, EUC-CN and Big5. These will get installed
as

perljp perlko perlcn perltw

o The documentation for the POSIX-BC platform is called
"BS2000", to avoid confusion with the Perl POSIX module.

o The documentation for the WinCE platform is called
perlce (README.ce in the source code kit), to avoid
confusion with the perlwin32 documentation on
8.3-restricted filesystems.

Performance Enhancements
o map() could get pathologically slow when the result list
it generates is larger than the source list. The
performance has been improved for common scenarios.
[561]

o sort() is also fully reentrant, in the sense that the
sort function can itself call sort(). This did not work
reliably in previous releases. [561]

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o sort() has been changed to use primarily mergesort
internally as opposed to the earlier quicksort. For
very small lists this may result in slightly slower
sorting times, but in general the speedup should be at
least 20%. Additional bonuses are that the worst case
behaviour of sort() is now better (in computer science
terms it now runs in time O(N log N), as opposed to
quicksort's Theta(N**2) worst-case run time behaviour),
and that sort() is now stable (meaning that elements
with identical keys will stay ordered as they were
before the sort). See the "sort" pragma for
information.

The story in more detail: suppose you want to serve
yourself a little slice of Pi.

@digits = ( 3,1,4,1,5,9 );

A numerical sort of the digits will yield (1,1,3,4,5,9),
as expected. Which 1 comes first is hard to know, since
one 1 looks pretty much like any other. You can regard
this as totally trivial, or somewhat profound. However,
if you just want to sort the even digits ahead of the
odd ones, then what will

sort { ($a % 2) <=> ($b % 2) } @digits;

yield? The only even digit, 4, will come first. But
how about the odd numbers, which all compare equal?
With the quicksort algorithm used to implement Perl 5.6
and earlier, the order of ties is left up to the sort.
So, as you add more and more digits of Pi, the order in
which the sorted even and odd digits appear will change.
and, for sufficiently large slices of Pi, the quicksort
algorithm in Perl 5.8 won't return the same results even
if reinvoked with the same input. The justification for
this rests with quicksort's worst case behavior. If you
run

sort { $a <=> $b } ( 1 .. $N , 1 .. $N );

(something you might approximate if you wanted to merge
two sorted arrays using sort), doubling $N doesn't just
double the quicksort time, it quadruples it. Quicksort
has a worst case run time that can grow like N**2, so-
called quadratic behaviour, and it can happen on
patterns that may well arise in normal use. You won't
notice this for small arrays, but you will notice it
with larger arrays, and you may not live long enough for
the sort to complete on arrays of a million elements.
So the 5.8 quicksort scrambles large arrays before
sorting them, as a statistical defence against quadratic

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behaviour. But that means if you sort the same large
array twice, ties may be broken in different ways.

Because of the unpredictability of tie-breaking order,
and the quadratic worst-case behaviour, quicksort was
almost replaced completely with a stable mergesort.
Stable means that ties are broken to preserve the
original order of appearance in the input array. So

sort { ($a % 2) <=> ($b % 2) } (3,1,4,1,5,9);

will yield (4,3,1,1,5,9), guaranteed. The even and odd
numbers appear in the output in the same order they
appeared in the input. Mergesort has worst case O(N log
N) behaviour, the best value attainable. And,
ironically, this mergesort does particularly well where
quicksort goes quadratic: mergesort sorts (1..$N,
1..$N) in O(N) time. But quicksort was rescued at the
last moment because it is faster than mergesort on
certain inputs and platforms. For example, if you
really don't care about the order of even and odd
digits, quicksort will run in O(N) time; it's very good
at sorting many repetitions of a small number of
distinct elements. The quicksort divide and conquer
strategy works well on platforms with relatively small,
very fast, caches. Eventually, the problem gets
whittled down to one that fits in the cache, from which
point it benefits from the increased memory speed.

Quicksort was rescued by implementing a sort pragma to
control aspects of the sort. The stable subpragma
forces stable behaviour, regardless of algorithm. The
_quicksort and _mergesort subpragmas are heavy-handed
ways to select the underlying implementation. The
leading "_" is a reminder that these subpragmas may not
survive beyond 5.8. More appropriate mechanisms for
selecting the implementation exist, but they wouldn't
have arrived in time to save quicksort.

o Hashes now use Bob Jenkins "One-at-a-Time" hashing key
algorithm ( http://burtleburtle.net/bob/hash/doobs.html
). This algorithm is reasonably fast while producing a
much better spread of values than the old hashing
algorithm (originally by Chris Torek, later tweaked by
Ilya Zakharevich). Hash values output from the
algorithm on a hash of all 3-char printable ASCII keys
comes much closer to passing the DIEHARD random number
generation tests. According to perlbench, this change
has not affected the overall speed of Perl.

o unshift() should now be noticeably faster.

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Installation and Configuration Improvements
Generic Improvements
o INSTALL now explains how you can configure Perl to use
64-bit integers even on non-64-bit platforms.

o Policy.sh policy change: if you are reusing a Policy.sh
file (see INSTALL) and you use Configure
-Dprefix=/foo/bar and in the old Policy $prefix eq
$siteprefix and $prefix eq $vendorprefix, all of them
will now be changed to the new prefix, /foo/bar.
(Previously only $prefix changed.) If you do not like
this new behaviour, specify prefix, siteprefix, and
vendorprefix explicitly.

o A new optional location for Perl libraries,
otherlibdirs, is available. It can be used for example
for vendor add-ons without disturbing Perl's own library
directories.

o In many platforms, the vendor-supplied 'cc' is too
stripped-down to build Perl (basically, 'cc' doesn't do
ANSI C). If this seems to be the case and 'cc' does not
seem to be the GNU C compiler 'gcc', an automatic
attempt is made to find and use 'gcc' instead.

o gcc needs to closely track the operating system release
to avoid build problems. If Configure finds that gcc was
built for a different operating system release than is
running, it now gives a clearly visible warning that
there may be trouble ahead.

o Since Perl 5.8 is not binary-compatible with previous
releases of Perl, Configure no longer suggests including
the 5.005 modules in @INC.

o Configure "-S" can now run non-interactively. [561]

o Configure support for pdp11-style memory models has been
removed due to obsolescence. [561]

o configure.gnu now works with options with whitespace in
them.

o installperl now outputs everything to STDERR.

o Because PerlIO is now the default on most platforms,
"-perlio" doesn't get appended to the $Config{archname}
(also known as $^O) anymore. Instead, if you explicitly
choose not to use perlio (Configure command line option
-Uuseperlio), you will get "-stdio" appended.

o Another change related to the architecture name is that

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"-64all" (-Duse64bitall, or "maximally 64-bit") is
appended only if your pointers are 64 bits wide. (To be
exact, the use64bitall is ignored.)

o In AFS installations, one can configure the root of the
AFS to be somewhere else than the default /afs by using
the Configure parameter "-Dafsroot=/some/where/else".

o APPLLIB_EXP, a lesser-known configuration-time
definition, has been documented. It can be used to
prepend site-specific directories to Perl's default
search path (@INC); see INSTALL for information.

o The version of Berkeley DB used when the Perl (and,
presumably, the DB_File extension) was built is now
available as @Config{qw(db_version_major
db_version_minor db_version_patch)} from Perl and as
"DB_VERSION_MAJOR_CFG DB_VERSION_MINOR_CFG
DB_VERSION_PATCH_CFG" from C.

o Building Berkeley DB3 for compatibility modes for DB,
NDBM, and ODBM has been documented in INSTALL.

o If you have CPAN access (either network or a local copy
such as a CD-ROM) you can during specify extra modules
to Configure to build and install with Perl using the
-Dextras=... option. See INSTALL for more details.

o In addition to config.over, a new override file,
config.arch, is available. This file is supposed to be
used by hints file writers for architecture-wide changes
(as opposed to config.over which is for site-wide
changes).

o If your file system supports symbolic links, you can
build Perl outside of the source directory by

mkdir perl/build/directory
cd perl/build/directory
sh /path/to/perl/source/Configure -Dmksymlinks ...

This will create in perl/build/directory a tree of
symbolic links pointing to files in
/path/to/perl/source. The original files are left
unaffected. After Configure has finished, you can just
say

make all test

and Perl will be built and tested, all in
perl/build/directory. [561]

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o For Perl developers, several new make targets for
profiling and debugging have been added; see perlhack.

o Use of the gprof tool to profile Perl has been
documented in perlhack. There is a make target
called "perl.gprof" for generating a gprofiled
Perl executable.

o If you have GCC 3, there is a make target called
"perl.gcov" for creating a gcoved Perl
executable for coverage analysis. See perlhack.

o If you are on IRIX or Tru64 platforms, new
profiling/debugging options have been added; see
perlhack for more information about pixie and
Third Degree.

o Guidelines of how to construct minimal Perl
installations have been added to INSTALL.

o The Thread extension is now not built at all under
ithreads ("Configure -Duseithreads") because it wouldn't
work anyway (the Thread extension requires being
Configured with "-Duse5005threads").

Note that the 5.005 threads are unsupported and
deprecated: if you have code written for the old threads
you should migrate it to the new ithreads model.

o The Gconvert macro ($Config{d_Gconvert}) used by perl
for stringifying floating-point numbers is now more
picky about using sprintf %.*g rules for the conversion.
Some platforms that used to use gcvt may now resort to
the slower sprintf.

o The obsolete method of making a special (e.g.,
debugging) flavor of perl by saying

make LIBPERL=libperld.a

has been removed. Use -DDEBUGGING instead.

New Or Improved Platforms
For the list of platforms known to support Perl, see
"Supported Platforms" in perlport.

o AIX dynamic loading should be now better supported.

o AIX should now work better with gcc, threads, and
64-bitness. Also the long doubles support in AIX should
be better now. See perlaix.

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o AtheOS ( http://www.atheos.cx/ ) is a new platform.

o BeOS has been reclaimed.

o The DG/UX platform now supports 5.005-style threads.
See perldgux.

o The DYNIX/ptx platform (also known as dynixptx) is
supported at or near osvers 4.5.2.

o EBCDIC platforms (z/OS (also known as OS/390), POSIX-BC,
and VM/ESA) have been regained. Many test suite tests
still fail and the co-existence of Unicode and EBCDIC
isn't quite settled, but the situation is much better
than with Perl 5.6. See perlos390, perlbs2000 (for
POSIX-BC), and perlvmesa for more information.

o Building perl with -Duseithreads or -Duse5005threads now
works under HP-UX 10.20 (previously it only worked under
10.30 or later). You will need a thread library package
installed. See README.hpux. [561]

o Mac OS Classic is now supported in the mainstream source
package (MacPerl has of course been available since perl
5.004 but now the source code bases of standard Perl and
MacPerl have been synchronised) [561]

o Mac OS X (or Darwin) should now be able to build Perl
even on HFS+ filesystems. (The case-insensitivity used
to confuse the Perl build process.)

o NCR MP-RAS is now supported. [561]

o All the NetBSD specific patches (except for the
installation specific ones) have been merged back to the
main distribution.

o NetWare from Novell is now supported. See perlnetware.

o NonStop-UX is now supported. [561]

o NEC SUPER-UX is now supported.

o All the OpenBSD specific patches (except for the
installation specific ones) have been merged back to the
main distribution.

o Perl has been tested with the GNU pth userlevel thread
package ( http://www.gnu.org/software/pth/pth.html ).
All thread tests of Perl now work, but not without
adding some yield()s to the tests, so while pth (and
other userlevel thread implementations) can be

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considered to be "working" with Perl ithreads, keep in
mind the possible non-preemptability of the underlying
thread implementation.

o Stratus VOS is now supported using Perl's native build
method (Configure). This is the recommended method to
build Perl on VOS. The older methods, which build
miniperl, are still available. See perlvos. [561+]

o The Amdahl UTS Unix mainframe platform is now supported.
[561]

o WinCE is now supported. See perlce.

o z/OS (formerly known as OS/390, formerly known as MVS
OE) now has support for dynamic loading. This is not
selected by default, however, you must specify -Dusedl
in the arguments of Configure. [561]

Selected Bug Fixes
Numerous memory leaks and uninitialized memory accesses have
been hunted down. Most importantly, anonymous subs used to
leak quite a bit. [561]

o The autouse pragma didn't work for
Multi::Part::Function::Names.

o caller() could cause core dumps in certain situations.
Carp was sometimes affected by this problem. In
particular, caller() now returns a subroutine name of
"(unknown)" for subroutines that have been removed from
the symbol table.

o chop(@list) in list context returned the characters
chopped in reverse order. This has been reversed to be
in the right order. [561]

o Configure no longer includes the DBM libraries (dbm,
gdbm, db, ndbm) when building the Perl binary. The only
exception to this is SunOS 4.x, which needs them. [561]

o The behaviour of non-decimal but numeric string
constants such as "0x23" was platform-dependent: in some
platforms that was seen as 35, in some as 0, in some as
a floating point number (don't ask). This was caused by
Perl's using the operating system libraries in a
situation where the result of the string to number
conversion is undefined: now Perl consistently handles
such strings as zero in numeric contexts.

o Several debugger fixes: exit code now reflects the
script exit code, condition "0" now treated correctly,

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the "d" command now checks line number, $. no longer
gets corrupted, and all debugger output now goes
correctly to the socket if RemotePort is set. [561]

o The debugger (perl5db.pl) has been modified to present a
more consistent commands interface, via
(CommandSet=580). perl5db.t was also added to test the
changes, and as a placeholder for further tests.

See perldebug.

o The debugger has a new "dumpDepth" option to control the
maximum depth to which nested structures are dumped.
The "x" command has been extended so that "x N EXPR"
dumps out the value of EXPR to a depth of at most N
levels.

o The debugger can now show lexical variables if you have
the CPAN module PadWalker installed.

o The order of DESTROYs has been made more predictable.

o Perl 5.6.0 could emit spurious warnings about
redefinition of dl_error() when statically building
extensions into perl. This has been corrected. [561]

o dprofpp -R didn't work.

o *foo{FORMAT} now works.

o Infinity is now recognized as a number.

o UNIVERSAL::isa no longer caches methods incorrectly.
(This broke the Tk extension with 5.6.0.) [561]

o Lexicals I: lexicals outside an eval "" weren't resolved
correctly inside a subroutine definition inside the eval
"" if they were not already referenced in the top level
of the eval""ed code.

o Lexicals II: lexicals leaked at file scope into
subroutines that were declared before the lexicals.

o Lexical warnings now propagating correctly between
scopes and into "eval "..."".

o "use warnings qw(FATAL all)" did not work as intended.
This has been corrected. [561]

o warnings::enabled() now reports the state of $^W
correctly if the caller isn't using lexical warnings.
[561]

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o Line renumbering with eval and "#line" now works. [561]

o Fixed numerous memory leaks, especially in eval "".

o Localised tied variables no longer leak memory

use Tie::Hash;
tie my %tied_hash => 'Tie::StdHash';

...

# Used to leak memory every time local() was called;
# in a loop, this added up.
local($tied_hash{Foo}) = 1;

o Localised hash elements (and %ENV) are correctly
unlocalised to not exist, if they didn't before they
were localised.

use Tie::Hash;
tie my %tied_hash => 'Tie::StdHash';

...

# Nothing has set the FOO element so far

{ local $tied_hash{FOO} = 'Bar' }

# This used to print, but not now.
print "exists!\n" if exists $tied_hash{FOO};

As a side effect of this fix, tied hash interfaces must
define the EXISTS and DELETE methods.

o mkdir() now ignores trailing slashes in the directory
name, as mandated by POSIX.

o Some versions of glibc have a broken modfl(). This
affects builds with "-Duselongdouble". This version of
Perl detects this brokenness and has a workaround for
it. The glibc release 2.2.2 is known to have fixed the
modfl() bug.

o Modulus of unsigned numbers now works (4063328477 %
65535 used to return 27406, instead of 27047). [561]

o Some "not a number" warnings introduced in 5.6.0
eliminated to be more compatible with 5.005. Infinity
is now recognised as a number. [561]

o Numeric conversions did not recognize changes in the
string value properly in certain circumstances. [561]

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o Attributes (such as :shared) didn't work with our().

o our() variables will not cause bogus "Variable will not
stay shared" warnings. [561]

o "our" variables of the same name declared in two sibling
blocks resulted in bogus warnings about "redeclaration"
of the variables. The problem has been corrected. [561]

o pack "Z" now correctly terminates the string with "\0".

o Fix password routines which in some shadow password
platforms (e.g. HP-UX) caused getpwent() to return every
other entry.

o The PERL5OPT environment variable (for passing command
line arguments to Perl) didn't work for more than a
single group of options. [561]

o PERL5OPT with embedded spaces didn't work.

o printf() no longer resets the numeric locale to "C".

o "qw(a\\b)" now parses correctly as 'a\\b': that is, as
three characters, not four. [561]

o pos() did not return the correct value within s///ge in
earlier versions. This is now handled correctly. [561]

o Printing quads (64-bit integers) with printf/sprintf now
works without the q L ll prefixes (assuming you are on a
quad-capable platform).

o Regular expressions on references and overloaded scalars
now work. [561+]

o Right-hand side magic (GMAGIC) could in many cases such
as string concatenation be invoked too many times.

o scalar() now forces scalar context even when used in
void context.

o SOCKS support is now much more robust.

o sort() arguments are now compiled in the right wantarray
context (they were accidentally using the context of the
sort() itself). The comparison block is now run in
scalar context, and the arguments to be sorted are
always provided list context. [561]

o Changed the POSIX character class "[[:space:]]" to
include the (very rarely used) vertical tab character.

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Added a new POSIX-ish character class "[[:blank:]]"
which stands for horizontal whitespace (currently, the
space and the tab).

o The tainting behaviour of sprintf() has been
rationalized. It does not taint the result of floating
point formats anymore, making the behaviour consistent
with that of string interpolation. [561]

o Some cases of inconsistent taint propagation (such as
within hash values) have been fixed.

o The RE engine found in Perl 5.6.0 accidentally
pessimised certain kinds of simple pattern matches.
These are now handled better. [561]

o Regular expression debug output (whether through "use re
'debug'" or via "-Dr") now looks better. [561]

o Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were
flawed. The bug has been fixed. [561]

o Use of $& could trigger a core dump under some
situations. This is now avoided. [561]

o The regular expression captured submatches ($1, $2, ...)
are now more consistently unset if the match fails,
instead of leaving false data lying around in them.
[561]

o readline() on files opened in "slurp" mode could return
an extra "" (blank line) at the end in certain
situations. This has been corrected. [561]

o Autovivification of symbolic references of special
variables described in perlvar (as in "${$num}") was
accidentally disabled. This works again now. [561]

o Sys::Syslog ignored the "LOG_AUTH" constant.

o $AUTOLOAD, sort(), lock(), and spawning subprocesses in
multiple threads simultaneously are now thread-safe.

o Tie::Array's SPLICE method was broken.

o Allow a read-only string on the left-hand side of a non-
modifying tr///.

o If "STDERR" is tied, warnings caused by "warn" and "die"
now correctly pass to it.

o Several Unicode fixes.

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o BOMs (byte order marks) at the beginning of Perl
files (scripts, modules) should now be
transparently skipped. UTF-16 and UCS-2 encoded
Perl files should now be read correctly.

o The character tables have been updated to
Unicode 3.2.0.

o Comparing with utf8 data does not magically
upgrade non-utf8 data into utf8. (This was a
problem for example if you were mixing data from
I/O and Unicode data: your output might have got
magically encoded as UTF-8.)

o Generating illegal Unicode code points such as
U+FFFE, or the UTF-16 surrogates, now also
generates an optional warning.

o "IsAlnum", "IsAlpha", and "IsWord" now match
titlecase.

o Concatenation with the "." operator or via
variable interpolation, "eq", "substr",
"reverse", "quotemeta", the "x" operator,
substitution with "s///", single-quoted UTF-8,
should now work.

o The "tr///" operator now works. Note that the
"tr///CU" functionality has been removed (but
see pack('U0', ...)).

o "eval "v200"" now works.

o Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading
to spurious warnings. This has been corrected.
[561]

o Zero entries were missing from the Unicode
classes such as "IsDigit".

o Large unsigned numbers (those above 2**31) could
sometimes lose their unsignedness, causing bogus results
in arithmetic operations. [561]

o The Perl parser has been stress tested using both random
input and Markov chain input and the few found crashes
and lockups have been fixed.

Platform Specific Changes and Fixes
o BSDI 4.*

Perl now works on post-4.0 BSD/OSes.

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o All BSDs

Setting $0 now works (as much as possible; see perlvar
for details).

o Cygwin

Numerous updates; currently synchronised with Cygwin
1.3.10.

o Previously DYNIX/ptx had problems in its Configure probe
for non-blocking I/O.

o EPOC

EPOC now better supported. See README.epoc. [561]

o FreeBSD 3.*

Perl now works on post-3.0 FreeBSDs.

o HP-UX

README.hpux updated; "Configure -Duse64bitall" now
works; now uses HP-UX malloc instead of Perl malloc.

o IRIX

Numerous compilation flag and hint enhancements;
accidental mixing of 32-bit and 64-bit libraries (a
doomed attempt) made much harder.

o Linux

o Long doubles should now work (see INSTALL).
[561]

o Linux previously had problems related to
sockaddrlen when using accept(), recvfrom() (in
Perl: recv()), getpeername(), and getsockname().

o Mac OS Classic

Compilation of the standard Perl distribution in Mac OS
Classic should now work if you have the Metrowerks
development environment and the missing Mac-specific
toolkit bits. Contact the macperl mailing list for
details.

o MPE/iX

MPE/iX update after Perl 5.6.0. See README.mpeix. [561]

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o NetBSD/threads: try installing the GNU pth (should be in
the packages collection, or
http://www.gnu.org/software/pth/), and Configure with
-Duseithreads.

o NetBSD/sparc

Perl now works on NetBSD/sparc.

o OS/2

Now works with usethreads (see INSTALL). [561]

o Solaris

64-bitness using the Sun Workshop compiler now works.

o Stratus VOS

The native build method requires at least VOS Release
14.5.0 and GNU C++/GNU Tools 2.0.1 or later. The Perl
pack function now maps overflowed values to +infinity
and underflowed values to -infinity.

o Tru64 (aka Digital UNIX, aka DEC OSF/1)

The operating system version letter now recorded in
$Config{osvers}. Allow compiling with gcc (previously
explicitly forbidden). Compiling with gcc still not
recommended because buggy code results, even with gcc
2.95.2.

o Unicos

Fixed various alignment problems that lead into core
dumps either during build or later; no longer dies on
math errors at runtime; now using full quad integers (64
bits), previously was using only 46 bit integers for
speed.

o VMS

See "Socket Extension Dynamic in VMS" and "IEEE-format
Floating Point Default on OpenVMS Alpha" for important
changes not otherwise listed here.

chdir() now works better despite a CRT bug; now works
with MULTIPLICITY (see INSTALL); now works with Perl's
malloc.

The tainting of %ENV elements via "keys" or "values" was
previously unimplemented. It now works as documented.

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The "waitpid" emulation has been improved. The worst
bug (now fixed) was that a pid of -1 would cause a
wildcard search of all processes on the system.

POSIX-style signals are now emulated much better on VMS
versions prior to 7.0.

The "system" function and backticks operator have
improved functionality and better error handling. [561]

File access tests now use current process privileges
rather than the user's default privileges, which could
sometimes result in a mismatch between reported access
and actual access. This improvement is only available
on VMS v6.0 and later.

There is a new "kill" implementation based on
"sys$sigprc" that allows older VMS systems (pre-7.0) to
use "kill" to send signals rather than simply force
exit. This implementation also allows later systems to
call "kill" from within a signal handler.

Iterative logical name translations are now limited to
10 iterations in imitation of SHOW LOGICAL and other
OpenVMS facilities.

o Windows

o Signal handling now works better than it used
to. It is now implemented using a Windows
message loop, and is therefore less prone to
random crashes.

o fork() emulation is now more robust, but still
continues to have a few esoteric bugs and
caveats. See perlfork for details. [561+]

o A failed (pseudo)fork now returns undef and sets
errno to EAGAIN. [561]

o The following modules now work on Windows:

ExtUtils::Embed [561]
IO::Pipe
IO::Poll
Net::Ping

o IO::File::new_tmpfile() is no longer limited to
32767 invocations per-process.

o Better chdir() return value for a non-existent
directory.

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o Compiling perl using the 64-bit Platform SDK
tools is now supported.

o The Win32::SetChildShowWindow() builtin can be
used to control the visibility of windows
created by child processes. See Win32 for
details.

o Non-blocking waits for child processes (or
pseudo-processes) are supported via
"waitpid($pid, &POSIX::WNOHANG)".

o The behavior of system() with multiple arguments
has been rationalized. Each unquoted argument
will be automatically quoted to protect
whitespace, and any existing whitespace in the
arguments will be preserved. This improves the
portability of system(@args) by avoiding the
need for Windows "cmd" shell specific quoting in
perl programs.

Note that this means that some scripts that may
have relied on earlier buggy behavior may no
longer work correctly. For example,
"system("nmake /nologo", @args)" will now
attempt to run the file "nmake /nologo" and will
fail when such a file isn't found. On the other
hand, perl will now execute code such as
"system("c:/Program Files/MyApp/foo.exe",
@args)" correctly.

o The perl header files no longer suppress common
warnings from the Microsoft Visual C++ compiler.
This means that additional warnings may now show
up when compiling XS code.

o Borland C++ v5.5 is now a supported compiler
that can build Perl. However, the generated
binaries continue to be incompatible with those
generated by the other supported compilers (GCC
and Visual C++). [561]

o Duping socket handles with open(F, ">&MYSOCK")
now works under Windows 9x. [561]

o Current directory entries in %ENV are now
correctly propagated to child processes. [561]

o New %ENV entries now propagate to subprocesses.
[561]

o Win32::GetCwd() correctly returns C:\ instead of

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C: when at the drive root. Other bugs in
chdir() and Cwd::cwd() have also been fixed.
[561]

o The makefiles now default to the features
enabled in ActiveState ActivePerl (a popular
Win32 binary distribution). [561]

o HTML files will now be installed in c:\perl\html
instead of c:\perl\lib\pod\html

o REG_EXPAND_SZ keys are now allowed in registry
settings used by perl. [561]

o Can now send() from all threads, not just the
first one. [561]

o ExtUtils::MakeMaker now uses $ENV{LIB} to search
for libraries. [561]

o Less stack reserved per thread so that more
threads can run concurrently. (Still 16M per
thread.) [561]

o "File::Spec->tmpdir()" now prefers C:/temp over
/tmp (works better when perl is running as
service).

o Better UNC path handling under ithreads. [561]

o wait(), waitpid(), and backticks now return the
correct exit status under Windows 9x. [561]

o A socket handle leak in accept() has been fixed.
[561]

New or Changed Diagnostics
Please see perldiag for more details.

o Ambiguous range in the transliteration operator (like
a-z-9) now gives a warning.

o chdir("") and chdir(undef) now give a deprecation
warning because they cause a possible unintentional
chdir to the home directory. Say chdir() if you really
mean that.

o Two new debugging options have been added: if you have
compiled your Perl with debugging, you can use the -DT
[561] and -DR options to trace tokenising and to add
reference counts to displaying variables, respectively.

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o The lexical warnings category "deprecated" is no longer
a sub-category of the "syntax" category. It is now a
top-level category in its own right.

o Unadorned dump() will now give a warning suggesting to
use explicit CORE::dump() if that's what really is
meant.

o The "Unrecognized escape" warning has been extended to
include "\8", "\9", and "\_". There is no need to
escape any of the "\w" characters.

o All regular expression compilation error messages are
now hopefully easier to understand both because the
error message now comes before the failed regex and
because the point of failure is now clearly marked by a
"<-- HERE" marker.

o Various I/O (and socket) functions like binmode(),
close(), and so forth now more consistently warn if they
are used illogically either on a yet unopened or on an
already closed filehandle (or socket).

o Using lstat() on a filehandle now gives a warning.
(It's a non-sensical thing to do.)

o The "-M" and "-m" options now warn if you didn't supply
the module name.

o If you in "use" specify a required minimum version,
modules matching the name and but not defining a
$VERSION will cause a fatal failure.

o Using negative offset for vec() in lvalue context is now
a warnable offense.

o Odd number of arguments to overload::constant now
elicits a warning.

o Odd number of elements in anonymous hash now elicits a
warning.

o The various "opened only for", "on closed", "never
opened" warnings drop the "main::" prefix for
filehandles in the "main" package, for example "STDIN"
instead of "main::STDIN".

o Subroutine prototypes are now checked more carefully,
you may get warnings for example if you have used non-
prototype characters.

o If an attempt to use a (non-blessed) reference as an

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array index is made, a warning is given.

o "push @a;" and "unshift @a;" (with no values to push or
unshift) now give a warning. This may be a problem for
generated and eval'ed code.

o If you try to "pack" in perlfunc a number less than 0 or
larger than 255 using the "C" format you will get an
optional warning. Similarly for the "c" format and a
number less than -128 or more than 127.

o pack "P" format now demands an explicit size.

o unpack "w" now warns of unterminated compressed
integers.

o Warnings relating to the use of PerlIO have been added.

o Certain regex modifiers such as "(?o)" make sense only
if applied to the entire regex. You will get an
optional warning if you try to do otherwise.

o Variable length lookbehind has not yet been implemented,
trying to use it will tell that.

o Using arrays or hashes as references (e.g. "%foo->{bar}"
has been deprecated for a while. Now you will get an
optional warning.

o Warnings relating to the use of the new restricted
hashes feature have been added.

o Self-ties of arrays and hashes are not supported and
fatal errors will happen even at an attempt to do so.

o Using "sort" in scalar context now issues an optional
warning. This didn't do anything useful, as the sort
was not performed.

o Using the /g modifier in split() is meaningless and will
cause a warning.

o Using splice() past the end of an array now causes a
warning.

o Malformed Unicode encodings (UTF-8 and UTF-16) cause a
lot of warnings, as does trying to use UTF-16 surrogates
(which are unimplemented).

o Trying to use Unicode characters on an I/O stream
without marking the stream's encoding (using open() or
binmode()) will cause "Wide character" warnings.

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o Use of v-strings in use/require causes a (backward)
portability warning.

o Warnings relating to the use interpreter threads and
their shared data have been added.

Changed Internals
o PerlIO is now the default.

o perlapi.pod (a companion to perlguts) now attempts to
document the internal API.

o You can now build a really minimal perl called
microperl. Building microperl does not require even
running Configure; "make -f Makefile.micro" should be
enough. Beware: microperl makes many assumptions, some
of which may be too bold; the resulting executable may
crash or otherwise misbehave in wondrous ways. For
careful hackers only.

o Added rsignal(), whichsig(), do_join(), op_clear,
op_null, ptr_table_clear(), ptr_table_free(),
sv_setref_uv(), and several UTF-8 interfaces to the
publicised API. For the full list of the available APIs
see perlapi.

o Made possible to propagate customised exceptions via
croak()ing.

o Now xsubs can have attributes just like subs. (Well, at
least the built-in attributes.)

o dTHR and djSP have been obsoleted; the former removed
(because it's a no-op) and the latter replaced with dSP.

o PERL_OBJECT has been completely removed.

o The MAGIC constants (e.g. 'P') have been macrofied (e.g.
"PERL_MAGIC_TIED") for better source code readability
and maintainability.

o The regex compiler now maintains a structure that
identifies nodes in the compiled bytecode with the
corresponding syntactic features of the original regex
expression. The information is attached to the new
"offsets" member of the "struct regexp". See perldebguts
for more complete information.

o The C code has been made much more "gcc -Wall" clean.
Some warning messages still remain in some platforms, so
if you are compiling with gcc you may see some warnings
about dubious practices. The warnings are being worked

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on.

o perly.c, sv.c, and sv.h have now been extensively
commented.

o Documentation on how to use the Perl source repository
has been added to Porting/repository.pod.

o There are now several profiling make targets.

Security Vulnerability Closed [561]
(This change was already made in 5.7.0 but bears repeating
here.) (5.7.0 came out before 5.6.1: the development branch
5.7 released earlier than the maintenance branch 5.6)

A potential security vulnerability in the optional suidperl
component of Perl was identified in August 2000. suidperl
is neither built nor installed by default. As of November
2001 the only known vulnerable platform is Linux, most
likely all Linux distributions. CERT and various vendors
and distributors have been alerted about the vulnerability.
See
http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
for more information.

The problem was caused by Perl trying to report a suspected
security exploit attempt using an external program,
/bin/mail. On Linux platforms the /bin/mail program had an
undocumented feature which when combined with suidperl gave
access to a root shell, resulting in a serious compromise
instead of reporting the exploit attempt. If you don't have
/bin/mail, or if you have 'safe setuid scripts', or if
suidperl is not installed, you are safe.

The exploit attempt reporting feature has been completely
removed from Perl 5.8.0 (and the maintenance release 5.6.1,
and it was removed also from all the Perl 5.7 releases), so
that particular vulnerability isn't there anymore. However,
further security vulnerabilities are, unfortunately, always
possible. The suidperl functionality is most probably going
to be removed in Perl 5.10. In any case, suidperl should
only be used by security experts who know exactly what they
are doing and why they are using suidperl instead of some
other solution such as sudo ( see
http://www.courtesan.com/sudo/ ).

New Tests
Several new tests have been added, especially for the lib
and ext subsections. There are now about 69 000 individual
tests (spread over about 700 test scripts), in the
regression suite (5.6.1 has about 11 700 tests, in 258 test
scripts) The exact numbers depend on the platform and Perl

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configuration used. Many of the new tests are of course
introduced by the new modules, but still in general Perl is
now more thoroughly tested.

Because of the large number of tests, running the regression
suite will take considerably longer time than it used to:
expect the suite to take up to 4-5 times longer to run than
in perl 5.6. On a really fast machine you can hope to
finish the suite in about 6-8 minutes (wallclock time).

The tests are now reported in a different order than in
earlier Perls. (This happens because the test scripts from
under t/lib have been moved to be closer to the
library/extension they are testing.)

Known Problems
The Compiler Suite Is Still Very Experimental
The compiler suite is slowly getting better but it continues
to be highly experimental. Use in production environments
is discouraged.

Localising Tied Arrays and Hashes Is Broken
local %tied_array;

doesn't work as one would expect: the old value is restored
incorrectly. This will be changed in a future release, but
we don't know yet what the new semantics will exactly be.
In any case, the change will break existing code that relies
on the current (ill-defined) semantics, so just avoid doing
this in general.

Building Extensions Can Fail Because Of Largefiles
Some extensions like mod_perl are known to have issues with
`largefiles', a change brought by Perl 5.6.0 in which file
offsets default to 64 bits wide, where supported. Modules
may fail to compile at all, or they may compile and work
incorrectly. Currently, there is no good solution for the
problem, but Configure now provides appropriate non-
largefile ccflags, ldflags, libswanted, and libs in the
%Config hash (e.g., $Config{ccflags_nolargefiles}) so the
extensions that are having problems can try configuring
themselves without the largefileness. This is admittedly
not a clean solution, and the solution may not even work at
all. One potential failure is whether one can (or, if one
can, whether it's a good idea to) link together at all
binaries with different ideas about file offsets; all this
is platform-dependent.

Modifying $_ Inside for(..)
for (1..5) { $_++ }

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works without complaint. It shouldn't. (You should be able
to modify only lvalue elements inside the loops.) You can
see the correct behaviour by replacing the 1..5 with 1, 2,
3, 4, 5.

mod_perl 1.26 Doesn't Build With Threaded Perl
Use mod_perl 1.27 or higher.

lib/ftmp-security tests warn 'system possibly insecure'
Don't panic. Read the 'make test' section of INSTALL
instead.

libwww-perl (LWP) fails base/date #51
Use libwww-perl 5.65 or later.

PDL failing some tests
Use PDL 2.3.4 or later.

Perl_get_sv
You may get errors like 'Undefined symbol "Perl_get_sv"' or
"can't resolve symbol 'Perl_get_sv'", or the symbol may be
"Perl_sv_2pv". This probably means that you are trying to
use an older shared Perl library (or extensions linked with
such) with Perl 5.8.0 executable. Perl used to have such a
subroutine, but that is no more the case. Check your shared
library path, and any shared Perl libraries in those
directories.

Sometimes this problem may also indicate a partial Perl
5.8.0 installation, see "Mac OS X dyld undefined symbols"
for an example and how to deal with it.

Self-tying Problems
Self-tying of arrays and hashes is broken in rather deep and
hard-to-fix ways. As a stop-gap measure to avoid people
from getting frustrated at the mysterious results (core
dumps, most often), it is forbidden for now (you will get a
fatal error even from an attempt).

A change to self-tying of globs has caused them to be
recursively referenced (see: "Two-Phased Garbage Collection"
in perlobj). You will now need an explicit untie to destroy
a self-tied glob. This behaviour may be fixed at a later
date.

Self-tying of scalars and IO thingies works.

ext/threads/t/libc
If this test fails, it indicates that your libc (C library)
is not threadsafe. This particular test stress tests the
localtime() call to find out whether it is threadsafe. See
perlthrtut for more information.

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Failure of Thread (5.005-style) tests
Note that support for 5.005-style threading is deprecated,
experimental and practically unsupported. In 5.10, it is
expected to be removed. You should migrate your code to
ithreads.

The following tests are known to fail due to fundamental
problems in the 5.005 threading implementation. These are
not new failures--Perl 5.005_0x has the same bugs, but
didn't have these tests.

../ext/B/t/xref.t 255 65280 14 12 85.71% 3-14
../ext/List/Util/t/first.t 255 65280 7 4 57.14% 2 5-7
../lib/English.t 2 512 54 2 3.70% 2-3
../lib/FileCache.t 5 1 20.00% 5
../lib/Filter/Simple/t/data.t 6 3 50.00% 1-3
../lib/Filter/Simple/t/filter_only. 9 3 33.33% 1-2 5
../lib/Math/BigInt/t/bare_mbf.t 1627 4 0.25% 8 11 1626-1627
../lib/Math/BigInt/t/bigfltpm.t 1629 4 0.25% 10 13 1628-
1629
../lib/Math/BigInt/t/sub_mbf.t 1633 4 0.24% 8 11 1632-1633
../lib/Math/BigInt/t/with_sub.t 1628 4 0.25% 9 12 1627-1628
../lib/Tie/File/t/31_autodefer.t 255 65280 65 32 49.23% 34-65
../lib/autouse.t 10 1 10.00% 4
op/flip.t 15 1 6.67% 15

These failures are unlikely to get fixed as 5.005-style
threads are considered fundamentally broken. (Basically
what happens is that competing threads can corrupt shared
global state, one good example being regular expression
engine's state.)

Timing problems
The following tests may fail intermittently because of
timing problems, for example if the system is heavily
loaded.

t/op/alarm.t
ext/Time/HiRes/HiRes.t
lib/Benchmark.t
lib/Memoize/t/expmod_t.t
lib/Memoize/t/speed.t

In case of failure please try running them manually, for
example

./perl -Ilib ext/Time/HiRes/HiRes.t

Tied/Magical Array/Hash Elements Do Not Autovivify
For normal arrays "$foo = \$bar[1]" will assign "undef" to
$bar[1] (assuming that it didn't exist before), but for
tied/magical arrays and hashes such autovivification does

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not happen because there is currently no way to catch the
reference creation. The same problem affects slicing over
non-existent indices/keys of a tied/magical array/hash.

Unicode in package/class and subroutine names does not work

One can have Unicode in identifier names, but not in
package/class or subroutine names. While some limited
functionality towards this does exist as of Perl 5.8.0, that
is more accidental than designed; use of Unicode for the
said purposes is unsupported.

One reason of this unfinishedness is its (currently)
inherent unportability: since both package names and
subroutine names may need to be mapped to file and directory
names, the Unicode capability of the filesystem becomes
important-- and there unfortunately aren't portable answers.

Platform Specific Problems
AIX
o If using the AIX native make command, instead of just
"make" issue "make all". In some setups the former has
been known to spuriously also try to run "make install".
Alternatively, you may want to use GNU make.

o In AIX 4.2, Perl extensions that use C++ functions that
use statics may have problems in that the statics are
not getting initialized. In newer AIX releases, this
has been solved by linking Perl with the libC_r library,
but unfortunately in AIX 4.2 the said library has an
obscure bug where the various functions related to time
(such as time() and gettimeofday()) return broken
values, and therefore in AIX 4.2 Perl is not linked
against libC_r.

o vac 5.0.0.0 May Produce Buggy Code For Perl

The AIX C compiler vac version 5.0.0.0 may produce buggy
code, resulting in a few random tests failing when run
as part of "make test", but when the failing tests are
run by hand, they succeed. We suggest upgrading to at
least vac version 5.0.1.0, that has been known to
compile Perl correctly. "lslpp -L|grep vac.C" will tell
you the vac version. See README.aix.

o If building threaded Perl, you may get compilation
warning from pp_sys.c:

"pp_sys.c", line 4651.39: 1506-280 (W) Function argument assignment between types "unsigned char*" and "const void*" is not allowed.

This is harmless; it is caused by the getnetbyaddr() and
getnetbyaddr_r() having slightly different types for

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their first argument.

Alpha systems with old gccs fail several tests
If you see op/pack, op/pat, op/regexp, or ext/Storable tests
failing in a Linux/alpha or *BSD/Alpha, it's probably time
to upgrade your gcc. gccs prior to 2.95.3 are definitely
not good enough, and gcc 3.1 may be even better. (RedHat
Linux/alpha with gcc 3.1 reported no problems, as did Linux
2.4.18 with gcc 2.95.4.) (In Tru64, it is preferable to use
the bundled C compiler.)

AmigaOS
Perl 5.8.0 doesn't build in AmigaOS. It broke at some point
during the ithreads work and we could not find Amiga experts
to unbreak the problems. Perl 5.6.1 still works for AmigaOS
(as does the 5.7.2 development release).

BeOS
The following tests fail on 5.8.0 Perl in BeOS Personal
5.03:

t/op/lfs............................FAILED at test 17
t/op/magic..........................FAILED at test 24
ext/Fcntl/t/syslfs..................FAILED at test 17
ext/File/Glob/t/basic...............FAILED at test 3
ext/POSIX/t/sigaction...............FAILED at test 13
ext/POSIX/t/waitpid.................FAILED at test 1

See perlbeos (README.beos) for more details.

Cygwin "unable to remap"
For example when building the Tk extension for Cygwin, you
may get an error message saying "unable to remap". This is
known problem with Cygwin, and a workaround is detailed in
here:
http://sources.redhat.com/ml/cygwin/2001-12/msg00894.html

Cygwin ndbm tests fail on FAT
One can build but not install (or test the build of) the
NDBM_File on FAT filesystems. Installation (or build) on
NTFS works fine. If one attempts the test on a FAT install
(or build) the following failures are expected:

../ext/NDBM_File/ndbm.t 13 3328 71 59 83.10% 1-2 4 16-71
../ext/ODBM_File/odbm.t 255 65280 ?? ?? % ??
../lib/AnyDBM_File.t 2 512 12 2 16.67% 1 4
../lib/Memoize/t/errors.t 0 139 11 5 45.45% 7-11
../lib/Memoize/t/tie_ndbm.t 13 3328 4 4 100.00% 1-4
run/fresh_perl.t 97 1 1.03% 91

NDBM_File fails and ODBM_File just coredumps.

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If you intend to run only on FAT (or if using AnyDBM_File on
FAT), run Configure with the -Ui_ndbm and -Ui_dbm options to
prevent NDBM_File and ODBM_File being built.

DJGPP Failures
t/op/stat............................FAILED at test 29
lib/File/Find/t/find.................FAILED at test 1
lib/File/Find/t/taint................FAILED at test 1
lib/h2xs.............................FAILED at test 15
lib/Pod/t/eol........................FAILED at test 1
lib/Test/Harness/t/strap-analyze.....FAILED at test 8
lib/Test/Harness/t/test-harness......FAILED at test 23
lib/Test/Simple/t/exit...............FAILED at test 1

The above failures are known as of 5.8.0 with native builds
with long filenames, but there are a few more if running
under dosemu because of limitations (and maybe bugs) of
dosemu:

t/comp/cpp...........................FAILED at test 3
t/op/inccode.........................(crash)

and a few lib/ExtUtils tests, and several hundred
Encode/t/Aliases.t failures that work fine with long
filenames. So you really might prefer native builds and
long filenames.

FreeBSD built with ithreads coredumps reading large directories

This is a known bug in FreeBSD 4.5's readdir_r(), it has
been fixed in FreeBSD 4.6 (see perlfreebsd
(README.freebsd)).

FreeBSD Failing locale Test 117 For ISO 8859-15 Locales
The ISO 8859-15 locales may fail the locale test 117 in
FreeBSD. This is caused by the characters \xFF (y with
diaeresis) and \xBE (Y with diaeresis) not behaving
correctly when being matched case-insensitively. Apparently
this problem has been fixed in the latest FreeBSD releases.
( http://www.freebsd.org/cgi/query-pr.cgi?pr=34308 )

IRIX fails ext/List/Util/t/shuffle.t or Digest::MD5
IRIX with MIPSpro 7.3.1.2m or 7.3.1.3m compiler may fail the
List::Util test ext/List/Util/t/shuffle.t by dumping core.
This seems to be a compiler error since if compiled with gcc
no core dump ensues, and no failures have been seen on the
said test on any other platform.

Similarly, building the Digest::MD5 extension has been known
to fail with "*** Termination code 139 (bu21)".

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The cure is to drop optimization level (Configure
-Doptimize=-O2).

HP-UX lib/posix Subtest 9 Fails When LP64-Configured
If perl is configured with -Duse64bitall, the successful
result of the subtest 10 of lib/posix may arrive before the
successful result of the subtest 9, which confuses the test
harness so much that it thinks the subtest 9 failed.

Linux with glibc 2.2.5 fails t/op/int subtest #6 with
-Duse64bitint
This is a known bug in the glibc 2.2.5 with long long
integers. (
http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=65612 )

Linux With Sfio Fails op/misc Test 48
No known fix.

Mac OS X
Please remember to set your environment variable LC_ALL to
"C" (setenv LC_ALL C) before running "make test" to avoid a
lot of warnings about the broken locales of Mac OS X.

The following tests are known to fail in Mac OS X 10.1.5
because of buggy (old) implementations of Berkeley DB
included in Mac OS X:

Failed Test Stat Wstat Total Fail Failed List of Failed
-------------------------------------------------------------------------
../ext/DB_File/t/db-btree.t 0 11 ?? ?? % ??
../ext/DB_File/t/db-recno.t 149 3 2.01% 61 63 65

If you are building on a UFS partition, you will also
probably see t/op/stat.t subtest #9 fail. This is caused by
Darwin's UFS not supporting inode change time.

Also the ext/POSIX/t/posix.t subtest #10 fails but it is
skipped for now because the failure is Apple's fault, not
Perl's (blocked signals are lost).

If you Configure with ithreads, ext/threads/t/libc.t will
fail. Again, this is not Perl's fault-- the libc of Mac OS X
is not threadsafe (in this particular test, the localtime()
call is found to be threadunsafe.)

Mac OS X dyld undefined symbols
If after installing Perl 5.8.0 you are getting warnings
about missing symbols, for example

dyld: perl Undefined symbols
_perl_sv_2pv
_perl_get_sv

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you probably have an old pre-Perl-5.8.0 installation (or
parts of one) in /Library/Perl (the undefined symbols used
to exist in pre-5.8.0 Perls). It seems that for some reason
"make install" doesn't always completely overwrite the files
in /Library/Perl. You can move the old Perl shared library
out of the way like this:

cd /Library/Perl/darwin/CORE
mv libperl.dylib libperlold.dylib

and then reissue "make install". Note that the above of
course is extremely disruptive for anything using the
/usr/local/bin/perl. If that doesn't help, you may have to
try removing all the .bundle files from beneath
/Library/Perl, and again "make install"-ing.

OS/2 Test Failures
The following tests are known to fail on OS/2 (for clarity
only the failures are shown, not the full error messages):

../lib/ExtUtils/t/Mkbootstrap.t 1 256 18 1 5.56% 8
../lib/ExtUtils/t/Packlist.t 1 256 34 1 2.94% 17
../lib/ExtUtils/t/basic.t 1 256 17 1 5.88% 14
lib/os2_process.t 2 512 227 2 0.88% 174 209
lib/os2_process_kid.t 227 2 0.88% 174 209
lib/rx_cmprt.t 255 65280 18 3 16.67% 16-18

op/sprintf tests 91, 129, and 130
The op/sprintf tests 91, 129, and 130 are known to fail on
some platforms. Examples include any platform using sfio,
and Compaq/Tandem's NonStop-UX.

Test 91 is known to fail on QNX6 (nto), because "sprintf
'%e',0" incorrectly produces 0.000000e+0 instead of
0.000000e+00.

For tests 129 and 130, the failing platforms do not comply
with the ANSI C Standard: lines 19ff on page 134 of ANSI
X3.159 1989, to be exact. (They produce something other
than "1" and "-1" when formatting 0.6 and -0.6 using the
printf format "%.0f"; most often, they produce "0" and
"-0".)

SCO
The socketpair tests are known to be unhappy in SCO
3.2v5.0.4:

ext/Socket/socketpair.t...............FAILED tests 15-45

Solaris 2.5
In case you are still using Solaris 2.5 (aka SunOS 5.5), you
may experience failures (the test core dumping) in

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lib/locale.t. The suggested cure is to upgrade your
Solaris.

Solaris x86 Fails Tests With -Duse64bitint
The following tests are known to fail in Solaris x86 with
Perl configured to use 64 bit integers:

ext/Data/Dumper/t/dumper.............FAILED at test 268
ext/Devel/Peek/Peek..................FAILED at test 7

SUPER-UX (NEC SX)
The following tests are known to fail on SUPER-UX:

op/64bitint...........................FAILED tests 29-30, 32-33, 35-36
op/arith..............................FAILED tests 128-130
op/pack...............................FAILED tests 25-5625
op/pow................................
op/taint..............................# msgsnd failed
../ext/IO/lib/IO/t/io_poll............FAILED tests 3-4
../ext/IPC/SysV/ipcsysv...............FAILED tests 2, 5-6
../ext/IPC/SysV/t/msg.................FAILED tests 2, 4-6
../ext/Socket/socketpair..............FAILED tests 12
../lib/IPC/SysV.......................FAILED tests 2, 5-6
../lib/warnings.......................FAILED tests 115-116, 118-119

The op/pack failure ("Cannot compress negative numbers at
op/pack.t line 126") is serious but as of yet unsolved. It
points at some problems with the signedness handling of the
C compiler, as do the 64bitint, arith, and pow failures.
Most of the rest point at problems with SysV IPC.

Term::ReadKey not working on Win32
Use Term::ReadKey 2.20 or later.

UNICOS/mk
o During Configure, the test

Guessing which symbols your C compiler and preprocessor define...

will probably fail with error messages like

CC-20 cc: ERROR File = try.c, Line = 3
The identifier "bad" is undefined.

bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
^

CC-65 cc: ERROR File = try.c, Line = 3
A semicolon is expected at this point.

This is caused by a bug in the awk utility of UNICOS/mk.
You can ignore the error, but it does cause a slight

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problem: you cannot fully benefit from the h2ph utility
(see h2ph) that can be used to convert C headers to Perl
libraries, mainly used to be able to access from Perl
the constants defined using C preprocessor, cpp.
Because of the above error, parts of the converted
headers will be invisible. Luckily, these days the need
for h2ph is rare.

o If building Perl with interpreter threads (ithreads),
the getgrent(), getgrnam(), and getgrgid() functions
cannot return the list of the group members due to a bug
in the multithreaded support of UNICOS/mk. What this
means is that in list context the functions will return
only three values, not four.

UTS
There are a few known test failures, see perluts
(README.uts).

VOS (Stratus)
When Perl is built using the native build process on VOS
Release 14.5.0 and GNU C++/GNU Tools 2.0.1, all attempted
tests either pass or result in TODO (ignored) failures.

VMS
There should be no reported test failures with a default
configuration, though there are a number of tests marked
TODO that point to areas needing further debugging and/or
porting work.

Win32
In multi-CPU boxes, there are some problems with the I/O
buffering: some output may appear twice.

XML::Parser not working
Use XML::Parser 2.31 or later.

z/OS (OS/390)
z/OS has rather many test failures but the situation is
actually much better than it was in 5.6.0; it's just that so
many new modules and tests have been added.

Failed Test Stat Wstat Total Fail Failed List of Failed
---------------------------------------------------------------------------
../ext/Data/Dumper/t/dumper.t 357 8 2.24% 311 314 325 327
331 333 337 339
../ext/IO/lib/IO/t/io_unix.t 5 4 80.00% 2-5
../ext/Storable/t/downgrade.t 12 3072 169 12 7.10% 14-15 46-47 78-79
110-111 150 161
../lib/ExtUtils/t/Constant.t 121 30976 48 48 100.00% 1-48
../lib/ExtUtils/t/Embed.t 9 9 100.00% 1-9
op/pat.t 922 7 0.76% 665 776 785 832-

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834 845
op/sprintf.t 224 3 1.34% 98 100 136
op/tr.t 97 5 5.15% 63 71-74
uni/fold.t 780 6 0.77% 61 169 196 661
710-711

The failures in dumper.t and downgrade.t are problems in the
tests, those in io_unix and sprintf are problems in the USS
(UDP sockets and printf formats). The pat, tr, and fold
failures are genuine Perl problems caused by EBCDIC (and in
the pat and fold cases, combining that with Unicode). The
Constant and Embed are probably problems in the tests (since
they test Perl's ability to build extensions, and that seems
to be working reasonably well.)

Unicode Support on EBCDIC Still Spotty
Though mostly working, Unicode support still has problem
spots on EBCDIC platforms. One such known spot are the
"\p{}" and "\P{}" regular expression constructs for code
points less than 256: the "pP" are testing for Unicode code
points, not knowing about EBCDIC.

Seen In Perl 5.7 But Gone Now
"Time::Piece" (previously known as "Time::Object") was
removed because it was felt that it didn't have enough value
in it to be a core module. It is still a useful module,
though, and is available from the CPAN.

Perl 5.8 unfortunately does not build anymore on AmigaOS;
this broke accidentally at some point. Since there are not
that many Amiga developers available, we could not get this
fixed and tested in time for 5.8.0. Perl 5.6.1 still works
for AmigaOS (as does the 5.7.2 development release).

The "PerlIO::Scalar" and "PerlIO::Via" (capitalised) were
renamed as "PerlIO::scalar" and "PerlIO::via" (all
lowercase) just before 5.8.0. The main rationale was to
have all core PerlIO layers to have all lowercase names.
The "plugins" are named as usual, for example
"PerlIO::via::QuotedPrint".

The "threads::shared::queue" and
"threads::shared::semaphore" were renamed as "Thread::Queue"
and "Thread::Semaphore" just before 5.8.0. The main
rationale was to have thread modules to obey normal naming,
"Thread::" (the "threads" and "threads::shared" themselves
are more pragma-like, they affect compile-time, so they stay
lowercase).

Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc

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newsgroup and the perl bug database at http://bugs.perl.org/
. There may also be information at http://www.perl.com/ ,
the Perl Home Page.

If you believe you have an unreported bug, please run the
perlbug program included with your release. Be sure to trim
your bug down to a tiny but sufficient test case. Your bug
report, along with the output of "perl -V", will be sent off
to perlbug@perl.org to be analysed by the Perl porting team.

ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.

HISTORY
Written by Jarkko Hietaniemi <jhi@iki.fi>.

NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2

Further information about this software can be found on the
open source community website at http://www.perl.org/.

perl v5.12.5 Last change: 2012-11-03 59