perl5201delta - what is new for perl v5.20.1


   This document describes differences between the 5.20.0 release and the
   5.20.1 release.

   If you are upgrading from an earlier release such as 5.18.0, first read
   perl5200delta, which describes differences between 5.18.0 and 5.20.0.

Incompatible Changes

   There are no changes intentionally incompatible with 5.20.0.  If any
   exist, they are bugs, and we request that you submit a report.  See
   "Reporting Bugs" below.

Performance Enhancements

   *   An optimization to avoid problems with COW and deliberately
       overallocated PVs has been disabled because it interfered with
       another, more important, optimization, causing a slowdown on some
       platforms.  [perl #121975]

   *   Returning a string from a lexical variable could be slow in some
       cases.  This has now been fixed.  [perl #121977]

Modules and Pragmata

   Updated Modules and Pragmata
   *   Config::Perl::V has been upgraded from version 0.20 to 0.22.

       The list of Perl versions covered has been updated and some flaws
       in the parsing have been fixed.

   *   Exporter has been upgraded from version 5.70 to 5.71.

       Illegal POD syntax in the documentation has been corrected.

   *   ExtUtils::CBuilder has been upgraded from version 0.280216 to

       Android builds now link to both -lperl and

   *   File::Copy has been upgraded from version 2.29 to 2.30.

       The documentation now notes that "copy" will not overwrite read-
       only files.

   *   Module::CoreList has been upgraded from version 3.11 to 5.020001.

       The list of Perl versions covered has been updated.

   *   The PathTools module collection has been upgraded from version 3.47
       to 3.48.

       Fallbacks are now in place when cross-compiling for Android and
       $Config::Config{sh} is not yet defined.  [perl #121963]

   *   PerlIO::via has been upgraded from version 0.14 to 0.15.

       A minor portability improvement has been made to the XS

   *   Unicode::UCD has been upgraded from version 0.57 to 0.58.

       The documentation includes many clarifications and fixes.

   *   utf8 has been upgraded from version 1.13 to 1.13_01.

       The documentation has some minor formatting improvements.

   *   version has been upgraded from version 0.9908 to 0.9909.

       External libraries and Perl may have different ideas of what the
       locale is.  This is problematic when parsing version strings if the
       locale's numeric separator has been changed.  Version parsing has
       been patched to ensure it handles the locales correctly.  [perl
       #121930] <>


   Changes to Existing Documentation

   *   "av_len" - Emphasize that this returns the highest index in the
       array, not the size of the array.  [perl #120386]

   *   Note that "SvSetSV" doesn't do set magic.

   *   "sv_usepvn_flags" - Fix documentation to mention the use of "NewX"
       instead of "malloc".  [perl #121869]

   *   Clarify where "NUL" may be embedded or is required to terminate a


   *   Clarify the meaning of "-B" and "-T".

   *   "-l" now notes that it will return false if symlinks aren't
       supported by the file system.  [perl #121523]

   *   Note that "each", "keys" and "values" may produce different
       orderings for tied hashes compared to other perl hashes.  [perl
       #121404] <>

   *   Note that "exec LIST" and "system LIST" may fall back to the shell
       on Win32.  Only "exec PROGRAM LIST" and "system PROGRAM LIST"
       indirect object syntax will reliably avoid using the shell.  This
       has also been noted in perlport.  [perl #122046]

   *   Clarify the meaning of "our".  [perl #122132]


   *   Explain various ways of modifying an existing SV's buffer.  [perl
       #116925] <>


   *   We now have a code of conduct for the p5p mailing list, as
       documented in "STANDARDS OF CONDUCT" in perlpolicy.


   *   The "/x" modifier has been clarified to note that comments cannot
       be continued onto the next line by escaping them.


   *   Mention the use of empty conditionals in "for"/"while" loops for
       infinite loops.


   *   Added a discussion of locale issues in XS code.


   The following additions or changes have been made to diagnostic output,
   including warnings and fatal error messages.  For the complete list of
   diagnostic messages, see perldiag.

   Changes to Existing Diagnostics
   *   Variable length lookbehind not implemented in regex m/%s/

       Information about Unicode behaviour has been added.

Configuration and Compilation

   *   Building Perl no longer writes to the source tree when configured
       with Configure's -Dmksymlinks option.  [perl #121585]

Platform Support

   Platform-Specific Notes
       Build support has been improved for cross-compiling in general and
       for Android in particular.

       Corrected architectures and version numbers used in configuration
       hints when building Perl.

       c99 options have been cleaned up, hints look for solstudio as well
       as SUNWspro, and support for native "setenv" has been added.

   VMS An old bug in feature checking, mainly affecting pre-7.3 systems,
       has been fixed.

       %I64d is now being used instead of %lld for MinGW.

Internal Changes

   *   Added "sync_locale" in perlapi.  Changing the program's locale
       should be avoided by XS code.  Nevertheless, certain non-Perl
       libraries called from XS, such as "Gtk" do so.  When this happens,
       Perl needs to be told that the locale has changed.  Use this
       function to do so, before returning to Perl.

Selected Bug Fixes

   *   A bug has been fixed where zero-length assertions and code blocks
       inside of a regex could cause "pos" to see an incorrect value.
       [perl #122460] <>

   *   Using "s///e" on tainted utf8 strings could issue bogus "Malformed
       UTF-8 character (unexpected end of string)" warnings.  This has now
       been fixed.  [perl #122148]

   *   "system" and friends should now work properly on more Android

       Due to an oversight, the value specified through -Dtargetsh to
       Configure would end up being ignored by some of the build process.
       This caused perls cross-compiled for Android to end up with
       defective versions of "system", "exec" and backticks: the commands
       would end up looking for /bin/sh instead of /system/bin/sh, and so
       would fail for the vast majority of devices, leaving $! as

   *   Many issues have been detected by Coverity
       <> and fixed.


   Perl 5.20.1 represents approximately 4 months of development since Perl
   5.20.0 and contains approximately 12,000 lines of changes across 170
   files from 36 authors.

   Excluding auto-generated files, documentation and release tools, there
   were approximately 2,600 lines of changes to 110 .pm, .t, .c and .h

   Perl continues to flourish into its third decade thanks to a vibrant
   community of users and developers.  The following people are known to
   have contributed the improvements that became Perl 5.20.1:

   Aaron Crane, Abigail, Alberto Simes, Alexandr Ciornii, Alexandre
   (Midnite) Jousset, Andrew Fresh, Andy Dougherty, Brian Fraser, Chris
   'BinGOs' Williams, Craig A. Berry, Daniel Dragan, David Golden, David
   Mitchell, H.Merijn Brand, James E Keenan, Jan Dubois, Jarkko
   Hietaniemi, John Peacock, kafka, Karen Etheridge, Karl Williamson,
   Lukas Mai, Matthew Horsfall, Michael Bunk, Peter Martini, Rafael
   Garcia-Suarez, Reini Urban, Ricardo Signes, Shirakata Kentaro, Smylers,
   Steve Hay, Thomas Sibley, Todd Rinaldo, Tony Cook, Vladimir Marek, Yves

   The list above is almost certainly incomplete as it is automatically
   generated from version control history.  In particular, it does not
   include the names of the (very much appreciated) contributors who
   reported issues to the Perl bug tracker.

   Many of the changes included in this version originated in the CPAN
   modules included in Perl's core.  We're grateful to the entire CPAN
   community for helping Perl to flourish.

   For a more complete list of all of Perl's historical contributors,
   please see the AUTHORS file in the Perl source distribution.

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.

   If the bug you are reporting has security implications, which make it
   inappropriate to send to a publicly archived mailing list, then please
   send it to  This points to a closed
   subscription unarchived mailing list, which includes all the core
   committers, who will be able to help assess the impact of issues,
   figure out a resolution, and help co-ordinate the release of patches to
   mitigate or fix the problem across all platforms on which Perl is
   supported.  Please only use this address for security issues in the
   Perl core, not for modules independently distributed on CPAN.


   The Changes file for an explanation of how to view 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.


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