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Ricardo SIGNES > perl-5.17.6 > perl5175delta


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Source   Latest Release: perl-5.17.11


perl5175delta - what is new for perl v5.17.5


This document describes differences between the 5.17.4 release and the 5.17.5 release.

If you are upgrading from an earlier release such as 5.17.3, first read perl5174delta, which describes differences between 5.17.3 and 5.17.4.

Core Enhancements ^

Upgrade to Unicode 6.2

Perl now supports the final version of Unicode 6.2. Earlier releases in the 5.17 series supported Unicode 6.2 beta versions. There were no substantive changes in the final Unicode 6.2 version from the most recent beta, included in Perl 5.17.4. A list of changes from Unicode 6.1 is at

Security ^

Avoid calling memset with a negative count

Poorly written perl code that allows an attacker to specify the count to perl's x string repeat operator can already cause a memory exhaustion denial-of-service attack. A flaw in versions of perl before 5.15.5 can escalate that into a heap buffer overrun; coupled with versions of glibc before 2.16, it possibly allows the execution of arbitrary code.

The flaw addressed to this commit has been assigned identifier CVE-2012-5195.

Incompatible Changes ^

New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes

Unicode has now withdrawn their previous recommendation for regular expressions to automatically handle cases where a single character can match multiple characters case-insensitively; for example, the letter LATIN SMALL LETTER SHARP S and the sequence ss. This is because it turns out to be impracticable to do this correctly in all circumstances. Because Perl has tried to do this as best it can, it will continue to do so. (We are considering an option to turn it off.) However, a new restriction is being added on such matches when they occur in [bracketed] character classes. People were specifying things such as /[\0-\xff]/i, and being surprised that it matches the two character sequence ss (since LATIN SMALL LETTER SHARP S occurs in this range). This behavior is also inconsistent with the using a property instead of a range: \p{Block=Latin1} also includes LATIN SMALL LETTER SHARP S, but /[\p{Block=Latin1}]/i does not match ss. The new rule is that for there to be a multi-character case-insensitive match within a bracketed character class, the character must be explicitly listed, and not as an end point of a range. This more closely obeys the Principle of Least Astonishment. See "Bracketed Character Classes" in perlrecharclass. Note that a bug [perl #89774], now fixed as part of this change, prevented the previous behavior from working fully.

Change to Warnings About Lexical Subroutines

The warnings category for lexical subroutines is now "experimental::lexical_subs", with two colons, not "experimental:lexical_subs";

Modules and Pragmata ^

Updated Modules and Pragmata

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.

Changes to Existing Diagnostics

Utility Changes ^


Platform Support ^

Discontinued Platforms


Support for MPE/IX has been removed.

Platform-Specific Notes


The option to build without USE_SOCKETS_AS_HANDLES has been removed.

Internal Changes ^

Selected Bug Fixes ^

Acknowledgements ^

Perl 5.17.5 represents approximately 4 weeks of development since Perl 5.17.4 and contains approximately 17,000 lines of changes across 310 files from 32 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 5.17.5:

Aaron Crane, Adrian M. Enache, Andy Dougherty, Brad Gilbert, Chris 'BinGOs' Williams, Colin Kuskie, Craig A. Berry, Daniel Dragan, David Golden, David Mitchell, Dominic Hargreaves, Eric Brine, Father Chrysostomos, Florian Ragwitz, H.Merijn Brand, James E Keenan, Jerry D. Hedden, Jesse Luehrs, Karl Williamson, Nicholas Clark, Niko Tyni, Paul Johnson, Peter Martini, Reini Urban, Ricardo Signes, Ruslan Zakirov, Sawyer X, Smylers, Steffen Müller, Steve Hay, Tony Cook, Yves Orton.

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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