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perl590delta (1)


perl590delta - what is new for perl v5.9.0


Please see following description for synopsis


Perl Programmers Reference Guide                  PERL590DELTA(1)

     perl590delta - what is new for perl v5.9.0

     This document describes differences between the 5.8.0
     release and the 5.9.0 release.

Incompatible Changes
  Hash Randomisation
     Mainly due to security reasons, the "random ordering" of
     hashes has been made even more random.  Previously while the
     order of hash elements from keys(), values(), and each() was
     essentially random, it was still repeatable.  Now, however,
     the order varies between different runs of Perl.

     Perl has never guaranteed any ordering of the hash keys, and
     the ordering has already changed several times during the
     lifetime of Perl 5.  Also, the ordering of hash keys has
     always been, and continues to be, affected by the insertion

     The added randomness may affect applications.

     One possible scenario is when output of an application has
     included hash data.  For example, if you have used the
     Data::Dumper module to dump data into different files, and
     then compared the files to see whether the data has changed,
     now you will have false positives since the order in which
     hashes are dumped will vary.  In general the cure is to sort
     the keys (or the values); in particular for Data::Dumper to
     use the "Sortkeys" option.  If some particular order is
     really important, use tied hashes: for example the
     Tie::IxHash module which by default preserves the order in
     which the hash elements were added.

     More subtle problem is reliance on the order of "global
     destruction".  That is what happens at the end of execution:
     Perl destroys all data structures, including user data.  If
     your destructors (the DESTROY subroutines) have assumed any
     particular ordering to the global destruction, there might
     be problems ahead.  For example, in a destructor of one
     object you cannot assume that objects of any other class are
     still available, unless you hold a reference to them.  If
     the environment variable PERL_DESTRUCT_LEVEL is set to a
     non-zero value, or if Perl is exiting a spawned thread, it
     will also destruct the ordinary references and the symbol
     tables that are no longer in use.  You can't call a class
     method or an ordinary function on a class that has been
     collected that way.

     The hash randomisation is certain to reveal hidden
     assumptions about some particular ordering of hash elements,

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     and outright bugs: it revealed a few bugs in the Perl core
     and core modules.

     To disable the hash randomisation in runtime, set the
     environment variable PERL_HASH_SEED to 0 (zero) before
     running Perl (for more information see "PERL_HASH_SEED" in
     perlrun), or to disable the feature completely in compile
     time, compile with "-DNO_HASH_SEED" (see INSTALL).

     See "Algorithmic Complexity Attacks" in perlsec for the
     original rationale behind this change.

  UTF-8 On Filehandles No Longer Activated By Locale
     In Perl 5.8.0 all filehandles, including the standard
     filehandles, were implicitly set to be in Unicode UTF-8 if
     the locale settings indicated the use of UTF-8.  This
     feature caused too many problems, so the feature was turned
     off and redesigned: see "Core Enhancements".

  Single-number v-strings are no longer v-strings before "=>"

     The version strings or v-strings (see "Version Strings" in
     perldata) feature introduced in Perl 5.6.0 has been a source
     of some confusion-- especially when the user did not want to
     use it, but Perl thought it knew better.  Especially
     troublesome has been the feature that before a "=>" a
     version string (a "v" followed by digits) has been
     interpreted as a v-string instead of a string literal.  In
     other words:

             %h = ( v65 => 42 );

     has meant since Perl 5.6.0

             %h = ( 'A' => 42 );

     (at least in platforms of ASCII progeny)  Perl 5.8.1
     restored the more natural interpretation

             %h = ( 'v65' => 42 );

     The multi-number v-strings like v65.66 and 65.66.67 still
     continue to be v-strings in Perl 5.8.

  (Win32) The -C Switch Has Been Repurposed
     The -C switch has changed in an incompatible way.  The old
     semantics of this switch only made sense in Win32 and only
     in the "use utf8" universe in 5.6.x releases, and do not
     make sense for the Unicode implementation in 5.8.0.  Since
     this switch could not have been used by anyone, it has been
     repurposed.  The behavior that this switch enabled in 5.6.x
     releases may be supported in a transparent, data-dependent

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     fashion in a future release.

     For the new life of this switch, see "UTF-8 no longer
     default under UTF-8 locales", and "-C" in perlrun.

  (Win32) The /d Switch Of cmd.exe
     Since version 5.8.1, perl uses the /d switch when running
     the cmd.exe shell internally for system(), backticks, and
     when opening pipes to external programs.  The extra switch
     disables the execution of AutoRun commands from the
     registry, which is generally considered undesirable when
     running external programs.  If you wish to retain
     compatibility with the older behavior, set PERL5SHELL in
     your environment to "cmd /x/c".

  The $* variable has been removed
     $*, which was deprecated in favor of the "/s" and "/m"
     regexp modifiers, has been removed.

Core Enhancements
     Perl 5.9.0 has experimental support for assertions.  Note
     that the user interface is not fully stabilized yet, and it
     may change until the 5.10.0 release.  A new command-line
     switch, -A, is used to activate assertions, which are
     declared with the "assertions" pragma.  See assertions.

  Defined-or operators
     A new operator "//" (defined-or) has been implemented.  The
     following statement:

         $a // $b

     is merely equivalent to

        defined $a ? $a : $b


        $c //= $d;

     can be used instead of

        $c = $d unless defined $c;

     This operator has the same precedence and associativity as
     "||".  It has a low-precedence counterpart, "err", which has
     the same precedence and associativity as "or".  Special care
     has been taken to ensure that those operators Do What You
     Mean while not breaking old code, but some edge cases
     involving the empty regular expression may now parse
     differently.  See perlop for details.

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  UTF-8 no longer default under UTF-8 locales
     In Perl 5.8.0 many Unicode features were introduced.   One
     of them was found to be of more nuisance than benefit: the
     automagic (and silent) "UTF-8-ification" of filehandles,
     including the standard filehandles, if the user's locale
     settings indicated use of UTF-8.

     For example, if you had "en_US.UTF-8" as your locale, your
     STDIN and STDOUT were automatically "UTF-8", in other words
     an implicit binmode(..., ":utf8") was made.  This meant that
     trying to print, say, chr(0xff), ended up printing the bytes
     0xc3 0xbf.  Hardly what you had in mind unless you were
     aware of this feature of Perl 5.8.0.  The problem is that
     the vast majority of people weren't: for example in RedHat
     releases 8 and 9 the default locale setting is UTF-8, so all
     RedHat users got UTF-8 filehandles, whether they wanted it
     or not.  The pain was intensified by the Unicode
     implementation of Perl 5.8.0 (still) having nasty bugs,
     especially related to the use of s/// and tr///.  (Bugs that
     have been fixed in 5.8.1)

     Therefore a decision was made to backtrack the feature and
     change it from implicit silent default to explicit conscious
     option.  The new Perl command line option "-C" and its
     counterpart environment variable PERL_UNICODE can now be
     used to control how Perl and Unicode interact at interfaces
     like I/O and for example the command line arguments.  See
     "-C" in perlrun and "PERL_UNICODE" in perlrun for more

  Unsafe signals again available
     In Perl 5.8.0 the so-called "safe signals" were introduced.
     This means that Perl no longer handles signals immediately
     but instead "between opcodes", when it is safe to do so.
     The earlier immediate handling easily could corrupt the
     internal state of Perl, resulting in mysterious crashes.

     However, the new safer model has its problems too.  Because
     now an opcode, a basic unit of Perl execution, is never
     interrupted but instead let to run to completion, certain
     operations that can take a long time now really do take a
     long time.  For example, certain network operations have
     their own blocking and timeout mechanisms, and being able to
     interrupt them immediately would be nice.

     Therefore perl 5.8.1 introduced a "backdoor" to restore the
     pre-5.8.0 (pre-5.7.3, really) signal behaviour.  Just set
     the environment variable PERL_SIGNALS to "unsafe", and the
     old immediate (and unsafe) signal handling behaviour
     returns.  See "PERL_SIGNALS" in perlrun and "Deferred
     Signals (Safe Signals)" in perlipc.

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     In completely unrelated news, you can now use safe signals
     with POSIX::SigAction.  See "POSIX::SigAction" in POSIX.

  Tied Arrays with Negative Array Indices
     Formerly, the indices passed to "FETCH", "STORE", "EXISTS",
     and "DELETE" methods in tied array class were always non-
     negative.  If the actual argument was negative, Perl would
     call FETCHSIZE implicitly and add the result to the index
     before passing the result to the tied array method.  This
     behaviour is now optional.  If the tied array class contains
     a package variable named $NEGATIVE_INDICES which is set to a
     true value, negative values will be passed to "FETCH",
     "STORE", "EXISTS", and "DELETE" unchanged.

  local ${$x}
     The syntaxes

             local ${$x}
             local @{$x}
             local %{$x}

     now do localise variables, given that the $x is a valid
     variable name.

  Unicode Character Database 4.0.0
     The copy of the Unicode Character Database included in Perl
     5.8 has been updated to 4.0.0 from 3.2.0.  This means for
     example that the Unicode character properties are as in
     Unicode 4.0.0.

  Miscellaneous Enhancements
     "unpack()" now defaults to unpacking the $_.

     "map" in void context is no longer expensive. "map" is now
     context aware, and will not construct a list if called in
     void context.

     If a socket gets closed by the server while printing to it,
     the client now gets a SIGPIPE.  While this new feature was
     not planned, it fell naturally out of PerlIO changes, and is
     to be considered an accidental feature.

     PerlIO::get_layers(FH) returns the names of the PerlIO
     layers active on a filehandle.

     PerlIO::via layers can now have an optional UTF8 method to
     indicate whether the layer wants to "auto-:utf8" the stream.

     utf8::is_utf8() has been added as a quick way to test
     whether a scalar is encoded internally in UTF-8 (Unicode).

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Modules and Pragmata
  Updated Modules And Pragmata
     The following modules and pragmata have been updated since
     Perl 5.8.0:

         In much better shape than it used to be.  Still far from
         perfect, but maybe worth a try.

         An optional feature, ":hireswallclock", now allows for
         high resolution wall clock times (uses Time::HiRes).

         See B::Bytecode.

         Now has bytes::substr.

         One can now have custom character name aliases.

         There is now a simple command line frontend to the module called cpan.

         A new option, Pair, allows choosing the separator
         between hash keys and values.

         Significant updates on the encoding pragma functionality
         (tr/// and the DATA filehandle, formats).

         If a filehandle has been marked as to have an encoding,
         unmappable characters are detected already during input,
         not later (when the corrupted data is being used).

         The ISO 8859-6 conversion table has been corrected (the
         0x30..0x39 erroneously mapped to U+0660..U+0669, instead
         of U+0030..U+0039).  The GSM 03.38 conversion did not
         handle escape sequences correctly.  The UTF-7 encoding
         has been added (making Encode feature-complete with

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         A lot of bugs have been fixed since v1.60, the version
         included in Perl v5.8.0. Especially noteworthy are the
         bug in Calc that caused div and mod to fail for some
         large values, and the fixes to the handling of bad

         Some new features were added, e.g. the broot() method,
         you can now pass parameters to config() to change some
         settings at runtime, and it is now possible to trap the
         creation of NaN and infinity.

         As usual, some optimizations took place and made the
         math overall a tad faster. In some cases, quite a lot
         faster, actually. Especially alternative libraries like
         Math::BigInt::GMP benefit from this. In addition, a lot
         of the quite clunky routines like fsqrt() and flog() are
         now much much faster.

         Diamond inheritance now works.

         Reading from non-string scalars (like the special
         variables, see perlvar) now works.

         Complete rewrite.  As a side-effect, no longer refuses
         to startup when run by root.

         New utilities: refaddr, isvstring, looks_like_number,

         Can now store code references (via B::Deparse, so not

         Earlier versions of the strict pragma did not check the
         parameters implicitly passed to its "import" (use) and
         "unimport" (no) routine.  This caused the false idiom
         such as:

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                 use strict qw(@ISA);
                 @ISA = qw(Foo);

         This however (probably) raised the false expectation
         that the strict refs, vars and subs were being enforced
         (and that @ISA was somehow "declared").  But the strict
         refs, vars, and subs are not enforced when using this
         false idiom.

         Starting from Perl 5.8.1, the above will cause an error
         to be raised.  This may cause programs which used to
         execute seemingly correctly without warnings and errors
         to fail when run under 5.8.1.  This happens because

                 use strict qw(@ISA);

         will now fail with the error:

                 Unknown 'strict' tag(s) '@ISA'

         The remedy to this problem is to replace this code with
         the correct idiom:

                 use strict;
                 use vars qw(@ISA);
                 @ISA = qw(Foo);

         Now much more picky about extra or missing output from
         test scripts.

         Use of nanosleep(), if available, allows mixing
         subsecond sleeps with alarms.

         Several fixes, for example for join() problems and
         memory leaks.  In some platforms (like Linux) that use
         glibc the minimum memory footprint of one ithread has
         been reduced by several hundred kilobytes.

         Many memory leaks have been fixed.


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         Now returns extra information.

Utility Changes
     The "h2xs" utility now produces a more modern layout:
     Foo-Bar/lib/Foo/ instead of Foo/Bar/  Also, the
     boilerplate test is now called t/Foo-Bar.t instead of t/1.t.

     The Perl debugger (lib/ has now been extensively
     documented and bugs found while documenting have been fixed.

     "perldoc" has been rewritten from scratch to be more robust
     and feature rich.

     "perlcc -B" works now at least somewhat better, while
     "perlcc -c" is rather more broken.  (The Perl compiler suite
     as a whole continues to be experimental.)

New Documentation
     perl573delta has been added to list the differences between
     the (now quite obsolete) development releases 5.7.2 and

     perl58delta and perl581delta have been added: these are the
     perldeltas of 5.8.0 and 5.8.1, detailing the differences
     respectively between 5.6.0 and 5.8.0, and between 5.8.0 and

     perlartistic has been added: it is the Artistic License in
     pod format, making it easier for modules to refer to it.

     perlcheat has been added: it is a Perl cheat sheet.

     perlgpl has been added: it is the GNU General Public License
     in pod format, making it easier for modules to refer to it.

     perlmacosx has been added to tell about the installation and
     use of Perl in Mac OS X.

     perlos400 has been added to tell about the installation and
     use of Perl in OS/400 PASE.

     perlreref has been added: it is a regular expressions quick

Installation and Configuration Improvements
     The Unix standard Perl location, /usr/bin/perl, is no longer
     overwritten by default if it exists.  This change was very
     prudent because so many Unix vendors already provide a
     /usr/bin/perl, but simultaneously many system utilities may
     depend on that exact version of Perl, so better not to
     overwrite it.

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     One can now specify installation directories for site and
     vendor man and HTML pages, and site and vendor scripts.  See

     One can now specify a destination directory for Perl
     installation by specifying the DESTDIR variable for "make
     install".  (This feature is slightly different from the
     previous "Configure -Dinstallprefix=...".)  See INSTALL.

     gcc versions 3.x introduced a new warning that caused a lot
     of noise during Perl compilation: "gcc
     -Ialreadyknowndirectory (warning: changing search order)".
     This warning has now been avoided by Configure weeding out
     such directories before the compilation.

     One can now build subsets of Perl core modules by using the
     Configure flags "-Dnoextensions=..." and
     "-Donlyextensions=...", see INSTALL.

  Platform-specific enhancements
     In Cygwin Perl can now be built with threads ("Configure
     -Duseithreads").  This works with both Cygwin 1.3.22 and
     Cygwin 1.5.3.

     In newer FreeBSD releases Perl 5.8.0 compilation failed
     because of trying to use malloc.h, which in FreeBSD is just
     a dummy file, and a fatal error to even try to use.  Now
     malloc.h is not used.

     Perl is now known to build also in Hitachi HI-UXMPP.

     Perl is now known to build again in LynxOS.

     Mac OS X now installs with Perl version number embedded in
     installation directory names for easier upgrading of user-
     compiled Perl, and the installation directories in general
     are more standard.  In other words, the default installation
     no longer breaks the Apple-provided Perl.  On the other
     hand, with "Configure -Dprefix=/usr" you can now really
     replace the Apple-supplied Perl (please be careful).

     Mac OS X now builds Perl statically by default.  This change
     was done mainly for faster startup times.  The Apple-
     provided Perl is still dynamically linked and shared, and
     you can enable the sharedness for your own Perl builds by
     "Configure -Duseshrplib".

     Perl has been ported to IBM's OS/400 PASE environment.  The
     best way to build a Perl for PASE is to use an AIX host as a
     cross-compilation environment.  See README.os400.

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     Yet another cross-compilation option has been added: now
     Perl builds on OpenZaurus, an Linux distribution based on
     Mandrake + Embedix for the Sharp Zaurus PDA.  See the
     Cross/README file.

     Tru64 when using gcc 3 drops the optimisation for toke.c to
     "-O2" because of gigantic memory use with the default "-O3".

     Tru64 can now build Perl with the newer Berkeley DBs.

     Building Perl on WinCE has been much enhanced, see README.ce
     and README.perlce.

Selected Bug Fixes
  Closures, eval and lexicals
     There have been many fixes in the area of anonymous subs,
     lexicals and closures.  Although this means that Perl is now
     more "correct", it is possible that some existing code will
     break that happens to rely on the faulty behaviour.  In
     practice this is unlikely unless your code contains a very
     complex nesting of anonymous subs, evals and lexicals.

  Generic fixes
     If an input filehandle is marked ":utf8" and Perl sees
     illegal UTF-8 coming in when doing "<FH>", if warnings are
     enabled a warning is immediately given - instead of being
     silent about it and Perl being unhappy about the broken data
     later.  (The ":encoding(utf8)" layer also works the same

     binmode(SOCKET, ":utf8") only worked on the input side, not
     on the output side of the socket.  Now it works both ways.

     For threaded Perls certain system database functions like
     getpwent() and getgrent() now grow their result buffer
     dynamically, instead of failing.  This means that at sites
     with lots of users and groups the functions no longer fail
     by returning only partial results.

     Perl 5.8.0 had accidentally broken the capability for users
     to define their own uppercase<->lowercase Unicode mappings
     (as advertised by the Camel).  This feature has been fixed
     and is also documented better.

     In 5.8.0 this

             $some_unicode .= <FH>;

     didn't work correctly but instead corrupted the data.  This
     has now been fixed.

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     Tied methods like FETCH etc. may now safely access tied
     values, i.e.  resulting in a recursive call to FETCH etc.
     Remember to break the recursion, though.

     At startup Perl blocks the SIGFPE signal away since there
     isn't much Perl can do about it.  Previously this blocking
     was in effect also for programs executed from within Perl.
     Now Perl restores the original SIGFPE handling routine,
     whatever it was, before running external programs.

     Linenumbers in Perl scripts may now be greater than 65536,
     or 2**16.  (Perl scripts have always been able to be larger
     than that, it's just that the linenumber for reported errors
     and warnings have "wrapped around".)  While scripts that
     large usually indicate a need to rethink your code a bit,
     such Perl scripts do exist, for example as results from
     generated code.  Now linenumbers can go all the way to
     4294967296, or 2**32.

  Platform-specific fixes

     o   Setting $0 works again (with certain limitations that
         Perl cannot do much about: see "$0" in perlvar)


     o   Setting $0 now works.


     o   Configuration now tests for the presence of "poll()",
         and IO::Poll now uses the vendor-supplied function if

     o   A rare access violation at Perl start-up could occur if
         the Perl image was installed with privileges or if there
         was an identifier with the subsystem attribute set in
         the process's rightslist.  Either of these circumstances
         triggered tainting code that contained a pointer bug.
         The faulty pointer arithmetic has been fixed.

     o   The length limit on values (not keys) in the %ENV hash
         has been raised from 255 bytes to 32640 bytes (except
         when the PERL_ENV_TABLES setting overrides the default
         use of logical names for %ENV).  If it is necessary to
         access these long values from outside Perl, be aware
         that they are implemented using search list logical
         names that store the value in pieces, each 255-byte
         piece (up to 128 of them) being an element in the search
         list. When doing a lookup in %ENV from within Perl, the
         elements are combined into a single value.  The existing

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         VMS-specific ability to access individual elements of a
         search list logical name via the $ENV{'foo;N'} syntax
         (where N is the search list index) is unimpaired.

     o   The piping implementation now uses local rather than
         global DCL symbols for inter-process communication.

     o   File::Find could become confused when navigating to a
         relative directory whose name collided with a logical
         name.  This problem has been corrected by adding
         directory syntax to relative path names, thus preventing
         logical name translation.


     o   A memory leak in the fork() emulation has been fixed.

     o   The return value of the ioctl() built-in function was
         accidentally broken in 5.8.0.  This has been corrected.

     o   The internal message loop executed by perl during
         blocking operations sometimes interfered with messages
         that were external to Perl.  This often resulted in
         blocking operations terminating prematurely or returning
         incorrect results, when Perl was executing under
         environments that could generate Windows messages.  This
         has been corrected.

     o   Pipes and sockets are now automatically in binary mode.

     o   The four-argument form of select() did not preserve $!
         (errno) properly when there were errors in the
         underlying call.  This is now fixed.

     o   The "CR CR LF" problem of has been fixed, binmode(FH,
         ":crlf") is now effectively a no-op.

New or Changed Diagnostics
     All the warnings related to pack() and unpack() were made
     more informative and consistent.

  Changed "A thread exited while %d threads were running"
     The old version

         A thread exited while %d other threads were still running

     was misleading because the "other" included also the thread
     giving the warning.

  Removed "Attempt to clear a restricted hash"
     It is not illegal to clear a restricted hash, so the warning
     was removed.

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  New "Illegal declaration of anonymous subroutine"
     You must specify the block of code for "sub".

  Changed "Invalid range "%s" in transliteration operator"
     The old version

         Invalid [] range "%s" in transliteration operator

     was simply wrong because there are no "[] ranges" in tr///.

  New "Missing control char name in \c"

  New "Newline in left-justified string for %s"
     The padding spaces would appear after the newline, which is
     probably not what you had in mind.

  New "Possible precedence problem on bitwise %c operator"
     If you think this

         $x & $y == 0

     tests whether the bitwise AND of $x and $y is zero, you will
     like this warning.

  New "read() on %s filehandle %s"
     You cannot read() (or sysread()) from a closed or unopened

  New "Tied variable freed while still in use"
     Something pulled the plug on a live tied variable, Perl
     plays safe by bailing out.

  New "To%s: illegal mapping '%s'"
     An illegal user-defined Unicode casemapping was specified.

  New "Use of freed value in iteration"
     Something modified the values being iterated over.  This is
     not good.

Changed Internals
     These news matter to you only if you either write XS code or
     like to know about or hack Perl internals (using Devel::Peek
     or any of the "B::" modules counts), or like to run Perl
     with the "-D" option.

     The embedding examples of perlembed have been reviewed to be
     up to date and consistent: for example, the correct use of

     Extensive reworking of the pad code (the code responsible
     for lexical variables) has been conducted by Dave Mitchell.

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     Extensive work on the v-strings by John Peacock.

     UTF-8 length and position cache: to speed up the handling of
     Unicode (UTF-8) scalars, a cache was introduced.  Potential
     problems exist if an extension bypasses the official APIs
     and directly modifies the PV of an SV: the UTF-8 cache does
     not get cleared as it should.

     APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn,
     sv_catsv, sv_setsv, are again available.

     Certain Perl core C APIs like cxinc and regatom are no
     longer available at all to code outside the Perl core of the
     Perl core extensions.  This is intentional.  They never
     should have been available with the shorter names, and if
     you application depends on them, you should (be ashamed and)
     contact perl5-porters to discuss what are the proper APIs.

     Certain Perl core C APIs like "Perl_list" are no longer
     available without their "Perl_" prefix.  If your XS module
     stops working because some functions cannot be found, in
     many cases a simple fix is to add the "Perl_" prefix to the
     function and the thread context "aTHX_" as the first
     argument of the function call.  This is also how it should
     always have been done: letting the Perl_-less forms to leak
     from the core was an accident.  For cleaner embedding you
     can also force this for all APIs by defining at compile time
     the cpp define PERL_NO_SHORT_NAMES.

     Perl_save_bool() has been added.

     Regexp objects (those created with "qr") now have S-magic
     rather than R-magic.  This fixed regexps of the form
     /...(??{...;$x})/ to no longer ignore changes made to $x.
     The S-magic avoids dropping the caching optimization and
     making (??{...}) constructs obscenely slow (and consequently
     useless).  See also "Magic Variables" in perlguts.
     Regexp::Copy was affected by this change.

     The Perl internal debugging macros DEBUG() and DEB() have
     been renamed to PERL_DEBUG() and PERL_DEB() to avoid
     namespace conflicts.

     "-DL" removed (the leaktest had been broken and unsupported
     for years, use alternative debugging mallocs or tools like
     valgrind and Purify).

     Verbose modifier "v" added for "-DXv" and "-Dsv", see

New Tests
     In Perl 5.8.0 there were about 69000 separate tests in about

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     700 test files, in Perl 5.9.0 there are about 77000 separate
     tests in about 780 test files.  The exact numbers depend on
     the Perl configuration and on the operating system platform.

Known Problems
     The hash randomisation mentioned in "Incompatible Changes"
     is definitely problematic: it will wake dormant bugs and
     shake out bad assumptions.

     Many of the rarer platforms that worked 100% or pretty close
     to it with perl 5.8.0 have been left a little bit untended
     since their maintainers have been otherwise busy lately, and
     therefore there will be more failures on those platforms.
     Such platforms include Mac OS Classic, IBM z/OS (and other
     EBCDIC platforms), and NetWare.  The most common Perl
     platforms (Unix and Unix-like, Microsoft platforms, and VMS)
     have large enough testing and expert population that they
     are doing well.

  Tied hashes in scalar context
     Tied hashes do not currently return anything useful in
     scalar context, for example when used as boolean tests:

             if (%tied_hash) { ... }

     The current nonsensical behaviour is always to return false,
     regardless of whether the hash is empty or has elements.

     The root cause is that there is no interface for the
     implementors of tied hashes to implement the behaviour of a
     hash in scalar context.

  Net::Ping 450_service and 510_ping_udp failures
     The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and
     the subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if
     you have an unusual networking setup.  For example in the
     latter case the test is trying to send a UDP ping to the IP

     The C-generating compiler backend B::C (the frontend being
     "perlcc -c") is even more broken than it used to be because
     of the extensive lexical variable changes.  (The good news
     is that B::Bytecode and ByteLoader are better than they used
     to be.)

Platform Specific Problems
  EBCDIC Platforms
     IBM z/OS and other EBCDIC platforms continue to be
     problematic regarding Unicode support.  Many Unicode tests
     are skipped when they really should be fixed.

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  Cygwin 1.5 problems
     In Cygwin 1.5 the io/tell and op/sysio tests have failures
     for some yet unknown reason.  In 1.5.5 the threads tests
     stress_cv, stress_re, and stress_string are failing unless
     the environment variable PERLIO is set to "perlio" (which
     makes also the io/tell failure go away).

     Perl 5.8.1 does build and work well with Cygwin 1.3: with
     (uname -a) "CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18
     09:20 i686 ..."  a 100% "make test"  was achieved with
     "Configure -des -Duseithreads".

  HP-UX: HP cc warnings about sendfile and sendpath
     With certain HP C compiler releases (e.g. B.11.11.02) you
     will get many warnings like this (lines wrapped for easier

       cc: "/usr/include/sys/socket.h", line 504: warning 562:
         Redeclaration of "sendfile" with a different storage class specifier:
           "sendfile" will have internal linkage.
       cc: "/usr/include/sys/socket.h", line 505: warning 562:
         Redeclaration of "sendpath" with a different storage class specifier:
           "sendpath" will have internal linkage.

     The warnings show up both during the build of Perl and
     during certain lib/ExtUtils tests that invoke the C
     compiler.  The warning, however, is not serious and can be

  IRIX: t/uni/tr_7jis.t falsely failing
     The test t/uni/tr_7jis.t is known to report failure under
     'make test' or the test harness with certain releases of
     IRIX (at least IRIX 6.5 and MIPSpro Compilers Version, but if run manually the test fully passes.

  Mac OS X: no usemymalloc
     The Perl malloc ("-Dusemymalloc") does not work at all in
     Mac OS X.  This is not that serious, though, since the
     native malloc works just fine.

  Tru64: No threaded builds with GNU cc (gcc)
     In the latest Tru64 releases (e.g. v5.1B or later) gcc
     cannot be used to compile a threaded Perl (-Duseithreads)
     because the system "<pthread.h>" file doesn't know about

  Win32: sysopen, sysread, syswrite
     As of the 5.8.0 release, sysopen()/sysread()/syswrite() do
     not behave like they used to in 5.6.1 and earlier with
     respect to "text" mode.  These built-ins now always operate
     in "binary" mode (even if sysopen() was passed the O_TEXT
     flag, or if binmode() was used on the file handle).  Note

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     that this issue should only make a difference for disk
     files, as sockets and pipes have always been in "binary"
     mode in the Windows port.  As this behavior is currently
     considered a bug, compatible behavior may be re-introduced
     in a future release.  Until then, the use of sysopen(),
     sysread() and syswrite() is not supported for "text" mode

     Here are some things that are planned for perl 5.10.0 :

     o   Various Copy-On-Write techniques will be investigated in
         hopes of speeding up Perl.

     o   CPANPLUS, Inline, and Module::Build will become core

     o   The ability to write true lexically scoped pragmas will
         be introduced, perhaps via a "pragma" pragma.

     o   Work will continue on the bytecompiler and byteloader.

     o   v-strings as they currently exist are scheduled to be
         deprecated.  The v-less form (1.2.3) will become a
         "version object" when used with "use", "require", and
         $VERSION.  $^V will also be a "version object" so the
         printf("%vd",...) construct will no longer be needed.
         The v-ful version (v1.2.3) will become obsolete.  The
         equivalence of strings and v-strings (e.g.  that
         currently 5.8.0 is equal to "\5\8\0") will go away.
         There may be no deprecation warning for v-strings,
         though: it is quite hard to detect when v-strings are
         being used safely, and when they are not.

Reporting Bugs
     If you find what you think is a bug, you might check the
     articles recently posted to the comp.lang.perl.misc
     newsgroup and the perl bug database at  There may also be information at, 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 to be analysed by the Perl porting team.
     You can browse and search the Perl 5 bugs at

     See attributes(5) for descriptions of the following

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     |Availability   | runtime/perl-512 |
     |Stability      | Uncommitted      |
     The Changes file for exhaustive details on what changed.

     The INSTALL file for how to build Perl.

     The README file for general stuff.

     The Artistic and Copying files for copyright information.

     This software was built from source available at  The original
     community source was downloaded from

     Further information about this software can be found on the
     open source community website at

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