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perl570delta (1)


perl570delta - what's new for perl v5.7.0


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Perl Programmers Reference Guide                  PERL570DELTA(1)

     perl570delta - what's new for perl v5.7.0

     This document describes differences between the 5.6.0
     release and the 5.7.0 release.

Security Vulnerability Closed
     A potential security vulnerability in the optional suidperl
     component of Perl has been identified.  suidperl is neither
     built nor installed by default.  As of September the 2nd,
     2000, the only known vulnerable platform is Linux, most
     likely all Linux distributions.  CERT and various vendors
     have been alerted about the vulnerability.

     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 the Perl 5.7.0 release, so that particular
     vulnerability isn't there anymore.  However, further
     security vulnerabilities are, unfortunately, always
     possible.  The suidperl code is being reviewed and if deemed
     too risky to continue to be supported, it may be completely
     removed from future releases.  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 ).

Incompatible Changes
     o   Arrays now always interpolate into double-quoted
         strings: constructs like "foo@bar" now always assume
         @bar is an array, whether or not the compiler has seen
         use of @bar.

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

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

     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

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         documented, tested and (most importantly) maintained.

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

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

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

     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.

     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', ...).

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

     o   my __PACKAGE__ $obj now works.

     o   "no Module;" now works even if there is no "sub
         unimport" in the Module.

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

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

     o   prototype(\&) is now available.

     o   There is now an UNTIE method.

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Modules and Pragmata
  New Modules
     o   File::Temp allows one to create temporary files and
         directories in an easy, portable, and secure way.

     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.

  Updated And Improved Modules and Pragmata
     o   The following independently supported modules have been
         updated to newer versions from CPAN: CGI, CPAN, DB_File,
         File::Spec, Getopt::Long, the podlators bundle,
         Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.

     o   Bug fixes and minor enhancements have been applied to
         B::Deparse, Data::Dumper, IO::Poll, IO::Socket::INET,
         Math::BigFloat, Math::Complex, Math::Trig,
         Net::protoent, the re pragma, SelfLoader, Sys::SysLog,
         Test::Harness, Text::Wrap, UNIVERSAL, and the warnings

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

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

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

                 use English '-no_performance_hit';

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

     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::Glob::glob() renamed to File::Glob::bsd_glob() to
         avoid prototype mismatch with CORE::glob().

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

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

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

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     o   The Shell module now has an OO interface.

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

     o   Perlbug is now much more robust.  It also sends the bug
         report to, not

     o   The perlcc utility has been rewritten and its user
         interface (that is, command line) is much more like that
         of the Unix C compiler, cc.

     o   The xsubpp utility for extension writers now understands
         POD documentation embedded in the *.xs files.

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

     o   perldebtut is a Perl debugging tutorial.

     o   perlebcdic contains considerations for running Perl on
         EBCDIC platforms.  Note that unfortunately EBCDIC
         platforms that used to supported back in Perl 5.005 are
         still unsupported by Perl 5.7.0; the plan, however, is
         to bring them back to the fold.

     o   perlnewmod tells about writing and submitting a new

     o   perlposix-bc explains using Perl on the POSIX-BC
         platform (an EBCDIC mainframe platform).

     o   perlretut is a regular expression tutorial.

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

     o   perlutil explains the command line utilities packaged
         with the Perl distribution.

Performance Enhancements
     o   map() that changes the size of the list should now work

     o   sort() has been changed to use 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

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         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).

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 change: if you are reusing a
         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

     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   If binary compatibility with the 5.005 release is not
         wanted, Configure no longer suggests including the 5.005
         modules in @INC.

     o   Configure "-S" can now run non-interactively.

     o   configure.gnu now works with options with whitespace in

     o   installperl now outputs everything to STDERR.

     o   $Config{byteorder} is now computed dynamically (this is
         more robust with "fat binaries" where an executable
         image contains binaries for more than one binary

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Selected Bug Fixes
     o   Several debugger fixes: exit code now reflects the
         script exit code, condition "0" now treated correctly,
         the "d" command now checks line number, the $. no longer
         gets corrupted, all debugger output now goes correctly
         to the socket if RemotePort is set.

     o   *foo{FORMAT} now works.

     o   Lexical warnings now propagating correctly between

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

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

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

     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.

     o   our() variables will not cause "will not stay shared"

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

     o   "q(a\\b)" now parses correctly as 'a\\b'.

     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.

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

     o   sort() arguments are now compiled in the right wantarray
         context (they were accidentally using the context of the
         sort() itself).

     o   Changed the POSIX character class "[[:space:]]" to
         include the (very rare) vertical tab character.  Added a

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

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

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

     o   Several Unicode fixes (but still not perfect).

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

         o       The character tables have been updated to
                 Unicode 3.0.1.

         o       chr() for values greater than 127 now create
                 utf8 when under use utf8.

         o       Comparing with utf8 data does not magically
                 upgrade non-utf8 data into utf8.

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

         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--in theory.

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

         o       vec() now refuses to deal with characters >255.

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

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

  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

     o   EPOC

         EPOC update after Perl 5.6.0.  See README.epoc.

     o   FreeBSD 3.*

         Perl now works on post-3.0 FreeBSDs.

     o   HP-UX

         README.hpux updated; "Configure -Duse64bitall" now
         almost works.

     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

         Long doubles should now work (see INSTALL).

     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

     o   MPE/iX

         MPE/iX update after Perl 5.6.0.  See README.mpeix.

     o   NetBSD/sparc

         Perl now works on NetBSD/sparc.

     o   OS/2

         Now works with usethreads (see INSTALL).

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     o   Solaris

         64-bitness using the Sun Workshop compiler now works.

     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

     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

     o   VMS

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

     o   Windows

         o       accept() no longer leaks memory.

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

         o       New %ENV entries now propagate to subprocesses.

         o       $ENV{LIB} now used to search for libs under
                 Visual C.

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

         o       Allow REG_EXPAND_SZ keys in the registry.

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

         o       Fake signal handling reenabled, bugs and all.

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

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

         o       Better UNC path handling under ithreads.

         o       wait() and waitpid() now work much better.

         o       winsock handle leak fixed.

New or Changed Diagnostics
     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.

     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

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

Changed Internals
     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() to the publicised

     o   Made possible to propagate customised exceptions via

     o   Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(),
         and utf8_to_bytes().

     o   Now xsubs can have attributes just like subs.

Known Problems
  Unicode Support Still Far From Perfect
     We're working on it.  Stay tuned.

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  EBCDIC Still A Lost Platform
     The plan is to bring them back.

  Building Extensions Can Fail Because Of Largefiles
     Certain extensions like mod_perl and BSD::Resource 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 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) link together at all binaries
     with different ideas about file offsets, all this is

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

  Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
     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.

  Long Doubles Still Don't Work In Solaris
     The experimental long double support is still very much so
     in Solaris.  (Other platforms like Linux and Tru64 are
     beginning to solidify in this area.)

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

  Storable tests fail in some platforms
     If any Storable tests fail the use of Storable is not

     o   Many Storable tests fail on AIX configured with 64 bit

         So far unidentified problems break Storable in AIX if
         Perl is configured to use 64 bit integers.  AIX in
         32-bit mode works and other 64-bit platforms work with

     o   DOS DJGPP may hang when testing Storable.

     o   st-06compat fails in UNICOS and UNICOS/mk.

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         This means that you cannot read old (pre-Storable-0.7)
         Storable images made in other platforms.

     o   st-store.t and st-retrieve may fail with Compaq C 6.2 on
         OpenVMS Alpha 7.2.

  Threads Are Still Experimental
     Multithreading is still an experimental feature.  Some
     platforms emit the following message for lib/thr5005

         # This is a KNOWN FAILURE, and one of the reasons why threading
         # is still an experimental feature.  It is here to stop people
         # from deploying threads in production. ;-)

     and another known thread-related warning is

        pragma/overload......Unbalanced saves: 3 more saves than restores
        panic: magic_mutexfree during global destruction.
        lib/selfloader.......Unbalanced saves: 3 more saves than restores
        panic: magic_mutexfree during global destruction.
        lib/st-dclone........Unbalanced saves: 3 more saves than restores
        panic: magic_mutexfree during global destruction.

  The Compiler Suite Is Still Experimental
     The compiler suite is slowly getting better but is nowhere
     near working order yet.  The backend part that has seen
     perhaps the most progress is the bytecode compiler.

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.

     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.

     Written by Jarkko Hietaniemi <>, with many
     contributions from The Perl Porters and Perl Users
     submitting feedback and patches.

     Send omissions or corrections to <>.

     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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