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perl51311delta - what is new for perl v5.13.11


This document describes differences between the 5.13.10 release and the 5.13.11 release.

If you are upgrading from an earlier release such as 5.13.9, first read perl5139delta, which describes differences between 5.13.9 and 5.13.10.


User-defined regular expression properties

Perl no longer allows a tainted regular expression to invoke a user-defined property via \p{...} syntax. It simply dies instead [perl #82616].

Incompatible Changes

local($_) will strip all magic from $_

local() on scalar variables will give them a new value, but keep all their magic intact. This has proven to be problematic for the default scalar variable $_, where perlsub recommends that any subroutine that assigns to $_ should localize it first. This would throw an exception if $_ is aliased to a read-only variable, and could have various unintentional side-effects in general.

Therefore, as an exception to the general rule, local($_) will not only assign a new value to $_, but also remove all existing magic from it as well.

Passing references to warn()

An earlier Perl 5.13.x release changed warn($ref) to leave the reference unchanged, allowing $SIG{__WARN__} handlers to access the original reference. But this stopped warnings that were references from having the file and line number appended even when there was no $SIG{__WARN__} handler in place.

Now warn checks for the presence of such a handler and, if there is none, proceeds to stringify the reference and append the file and line number. This allows simple uses of warn for debugging to continue to work as they did before.

fork() emulation will not wait for signalled children

On Windows parent processes would not terminate until all forked childred had terminated first. However, kill('KILL', ...) is inherently unstable on pseudo-processes, and kill('TERM', ...) might not get delivered if the child if blocked in a system call.

To avoid the deadlock and still provide a safe mechanism to terminate the hosting process, Perl will now no longer wait for children that have been sent a SIGTERM signal. It is up to the parent process to waitpid() for these children if child clean-up processing must be allowed to finish. However, it is also the responsibility of the parent then to avoid the deadlock by making sure the child process can't be blocked on I/O either.

See perlfork for more information about the fork() emulation on Windows.

Perl source code is read in text mode on Windows

Perl scripts used to be read in binary mode on Windows for the benefit of the ByteLoader module (which is no longer part of core Perl). This had the side effect of breaking various operations on the DATA filehandle, including seek()/tell(), and even simply reading from DATA after file handles have been flushed by a call to system(), backticks, fork() etc.

The default build options for Windows have been changed to read Perl source code on Windows in text mode now. Hopefully ByteLoader will be updated on CPAN to automatically handle this situation.

Performance Enhancements

Modules and Pragmata

Updated Modules and Pragmata


Changes to Existing Documentation



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


Many of the tests have been refactored to use testing libraries more consistently. In some cases test files were created or deleted:

Selected Bug Fixes


Perl 5.13.11 represents approximately one month of development since Perl 5.13.10 and contains approximately 80,000 lines of changes across 549 files from 31 authors and committers:

Alastair Douglas, Arvan, Boris Ratner, brian d foy, Chris 'BinGOs' Williams, Craig A. Berry, David Golden, David Leadbeater, David Mitchell, Father Chrysostomos, Florian Ragwitz, Jan Dubois, Karl Williamson, Kevin Ryde, Leon Brocard, Leon Timmermans, Michael Stevens, Michael Witten, Moritz Lenz, Nicholas Clark, Paul Johnson, Peter John Acklam, Reini Urban, Robin Barker, Steve Hay, Sullivan Beck, Tony Cook, Vadim Konovalov, Yves Orton, Zefram and Ævar Arnfjörð Bjarmason

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 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.