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perl5173delta - what is new for perl v5.17.3


This document describes differences between the 5.17.2 release and the 5.17.3 release.

If you are upgrading from an earlier release such as 5.17.1, first read perl5172delta, which describes differences between 5.17.1 and 5.17.2.

Core Enhancements ^

Computed Labels

The loop controls next, last and redo, and the special dump operator, now allow arbitrary expressions to be used to compute labels at run time. Previously, any argument that was not a constant was treated as the empty string.

Incompatible Changes ^

$ENV{foo}=undef deletes value from environ, like delete $ENV{foo}

This facilitates use of local() with %ENV entries. In previous versions of Perl, undef was converted to the empty string.

Defined values stored in environment are forced to byte strings

A value stored in an environment variable has always been stringified. In this release, it is converted to be only a byte string. First, it is forced to be a only a string. Then if the string is utf8 and the equivalent of utf8::downgrade() works, that result is used; otherwise, the equivalent of utf8::encode() is used, and a warning is issued about wide characters ("Diagnostics").

given now aliases the global $_

Instead of assigning to an implicit lexical $_, given now makes the global $_ an alias for its argument, just like foreach. However, it still uses lexical $_ if there is lexical $_ in scope (again, just like foreach) [perl #114020].

Modules and Pragmata ^

Updated Modules and Pragmata

Documentation ^

Changes to Existing Documentation

perlfunc, perlop


Diagnostics ^

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.

New Diagnostics

New Errors

New Warnings

Configuration and Compilation ^

Platform Support ^

Discontinued Platforms

UTS Global

Support code relating to UTS global has been removed. UTS was a mainframe version of System V created by Amdahl, subsequently sold to UTS Global. The port has not been touched since before Perl 5.8.0, and UTS Global is now defunct.

Platform-Specific Notes


A new makefile option, USE_64_BIT_INT, has been added to the Windows makefiles. Set this to "define" when building a 32-bit perl if you want it to use 64-bit integers.

Machine code size reductions, already made to the DLLs of XS modules in Perl 5.17.2, have now been extended to the perl DLL itself.

Building with VC++ 6.0 was inadvertently broken in Perl 5.17.2 but has now been fixed again.


The a2p build has been fixed for the HP C++ compiler on OpenVMS.

Selected Bug Fixes ^

Acknowledgements ^

Perl 5.17.3 represents approximately 4 weeks of development since Perl 5.17.2 and contains approximately 85,000 lines of changes across 470 files from 24 authors.

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 5.17.3:

Andy Dougherty, Chip Salzenberg, Chris 'BinGOs' Williams, Craig A. Berry, Daniel Dragan, Dave Rolsky, David Leadbeater, David Mitchell, Eric Brine, Father Chrysostomos, Goro Fuji, James E Keenan, Jan Dubois, Joaquin Ferrero, Karl Williamson, Nicholas Clark, Paul Marquess, Reini Urban, Ricardo Signes, Robin Barker, Shirakata Kentaro, Steffen Müller, Steve Hay, Tony Cook.

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 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.

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