Jeffrey Ryan Thalhammer > Perl-Critic-1.120 > Perl::Critic::Policy::Variables::RequireLocalizedPunctuationVars



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Module Version: 1.120   Source   Latest Release: Perl-Critic-1.126


Perl::Critic::Policy::Variables::RequireLocalizedPunctuationVars - Magic variables should be assigned as "local".


This Policy is part of the core Perl::Critic distribution.


Punctuation variables (and their equivalents) are global variables. Messing with globals is dangerous in a complex program as it can lead to very subtle and hard to fix bugs. If you must change a magic variable in a non-trivial program, do it in a local scope.

For example, to slurp a filehandle into a scalar, it's common to set the record separator to undef instead of a newline. If you choose to do this (instead of using File::Slurp!) then be sure to localize the global and change it for as short a time as possible.

    # BAD:
    $/ = undef;
    my $content = <$fh>;

    # BETTER:
    my $content;
        local $/ = undef;
        $content = <$fh>;

    # A popular idiom:
    my $content = do { local $/ = undef; <$fh> };

This policy also allows the use of my. Perl prevents using my with "proper" punctuation variables, but allows $a, @ARGV, the names declared by English, etc. This is not a good coding practice, however it is not the concern of this specific policy to complain about that.

There are exemptions for $_ and @_, and the English equivalent $ARG.


You can configure your own exemptions using the allow option:

    allow = @ARGV $ARGV

These are added to the default exemptions.


Initial development of this policy was supported by a grant from the Perl Foundation.


Chris Dolan <>


Copyright (c) 2007-2011 Chris Dolan. Many rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module.

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