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177 PAUSE users
171 non-PAUSE users.

Steve Hay
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[ this is a template for a new perldelta file. Any text flagged as XXX needs to be processed before release. ]

perldelta - what is new for perl v5.20.0


This document describes differences between the 5.18.0 release and the 5.20.0 release.

If you are upgrading from an earlier release such as 5.16.0, first read perl5180delta, which describes differences between 5.16.0 and 5.18.0.


XXX Any important notices here

Core Enhancements

XXX New core language features go here. Summarize user-visible core language enhancements. Particularly prominent performance optimisations could go here, but most should go in the "Performance Enhancements" section.

[ List each enhancement as a =head2 entry ]


XXX Any security-related notices go here. In particular, any security vulnerabilities closed should be noted here rather than in the "Selected Bug Fixes" section.

[ List each security issue as a =head2 entry ]

Incompatible Changes

XXX For a release on a stable branch, this section aspires to be:

    There are no changes intentionally incompatible with 5.XXX.XXX
    If any exist, they are bugs, and we request that you submit a
    report.  See L</Reporting Bugs> below.

[ List each incompatible change as a =head2 entry ]


XXX Any deprecated features, syntax, modules etc. should be listed here.

Module removals

XXX Remove this section if inapplicable.

The following modules will be removed from the core distribution in a future release, and will at that time need to be installed from CPAN. Distributions on CPAN which require these modules will need to list them as prerequisites.

The core versions of these modules will now issue "deprecated"-category warnings to alert you to this fact. To silence these deprecation warnings, install the modules in question from CPAN.

Note that these are (with rare exceptions) fine modules that you are encouraged to continue to use. Their disinclusion from core primarily hinges on their necessity to bootstrapping a fully functional, CPAN-capable Perl installation, not usually on concerns over their design.

    XXX Note that deprecated modules should be listed here even if they are listed as an updated module in the "Modules and Pragmata" section.

[ List each other deprecation as a =head2 entry ]

Performance Enhancements

XXX Changes which enhance performance without changing behaviour go here. There may well be none in a stable release.

[ List each enhancement as a =item entry ]

  • XXX

Modules and Pragmata

XXX All changes to installed files in cpan/, dist/, ext/ and lib/ go here. If Module::CoreList is updated, generate an initial draft of the following sections using Porting/corelist-perldelta.pl, which prints stub entries to STDOUT. Results can be pasted in place of the '=head2' entries below. A paragraph summary for important changes should then be added by hand. In an ideal world, dual-life modules would have a Changes file that could be cribbed.

[ Within each section, list entries as a =item entry ]

New Modules and Pragmata

  • XXX

Updated Modules and Pragmata

  • XXX has been upgraded from version A.xx to B.yy.

Removed Modules and Pragmata

  • XXX


XXX Changes to files in pod/ go here. Consider grouping entries by file and be sure to link to the appropriate page, e.g. perlfunc.

New Documentation

XXX Changes which create new files in pod/ go here.


XXX Description of the purpose of the new file here

Changes to Existing Documentation

XXX Changes which significantly change existing files in pod/ go here. However, any changes to pod/perldiag.pod should go in the "Diagnostics" section.


  • XXX Description of the change here


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.

XXX New or changed warnings emitted by the core's C code go here. Also include any changes in perldiag that reconcile it to the C code.

New Diagnostics

XXX Newly added diagnostic messages go under here, separated into New Errors and New Warnings

New Errors

New Warnings

Changes to Existing Diagnostics

XXX Changes (i.e. rewording) of diagnostic messages go here

  • XXX Describe change here

Utility Changes

XXX Changes to installed programs such as perlbug and xsubpp go here. Most of these are built within the directories utils and x2p.

[ List utility changes as a =head3 entry for each utility and =item entries for each change Use XXX with program names to get proper documentation linking. ]


  • XXX

Configuration and Compilation

XXX Changes to Configure, installperl, installman, and analogous tools go here. Any other changes to the Perl build process should be listed here. However, any platform-specific changes should be listed in the "Platform Support" section, instead.

[ List changes as a =item entry ].

  • XXX


XXX Any significant changes to the testing of a freshly built perl should be listed here. Changes which create new files in t/ go here as do any large changes to the testing harness (e.g. when parallel testing was added). Changes to existing files in t/ aren't worth summarizing, although the bugs that they represent may be covered elsewhere.

[ List each test improvement as a =item entry ]

  • XXX

Platform Support

XXX Any changes to platform support should be listed in the sections below.

[ Within the sections, list each platform as a =item entry with specific changes as paragraphs below it. ]

New Platforms

XXX List any platforms that this version of perl compiles on, that previous versions did not. These will either be enabled by new files in the hints/ directories, or new subdirectories and README files at the top level of the source tree.



Discontinued Platforms

XXX List any platforms that this version of perl no longer compiles on.



Platform-Specific Notes

XXX List any changes for specific platforms. This could include configuration and compilation changes or changes in portability/compatibility. However, changes within modules for platforms should generally be listed in the "Modules and Pragmata" section.



Internal Changes

XXX Changes which affect the interface available to XS code go here. Other significant internal changes for future core maintainers should be noted as well.

[ List each change as a =item entry ]

  • XXX

Selected Bug Fixes

XXX Important bug fixes in the core language are summarized here. Bug fixes in files in ext/ and lib/ are best summarized in "Modules and Pragmata".

[ List each fix as a =item entry ]

  • XXX

Known Problems

XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any tests that had to be TODOed for the release would be noted here. Unfixed platform specific bugs also go here.

[ List each fix as a =item entry ]

  • The following modules are known to have test failures with this version of Perl. Patches have been submitted, so there will hopefully be new releases soon:

    XXX Go through this list just before the release of 5.20 and remove any modules that have been fixed.


XXX If any significant core contributor has died, we've added a short obituary here.


XXX Generate this with:

  perl Porting/acknowledgements.pl v5.19.5..HEAD

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 http://rt.perl.org/perlbug/ . There may also be information at http://www.perl.org/ , 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.

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 perl5-security-report@perl.org. 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.