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Perl::Critic::Policy::Variables::RequireLocalizedPunctuationVars.3pm

NAME

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

AFFILIATION

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

DESCRIPTION

Punctuation variables (and their English.pm 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.

CONFIGURATION

You can configure your own exemptions using the "allow" option:

     [Variables::RequireLocalizedPunctuationVars]
     allow = @ARGV $ARGV
 
 

These are added to the default exemptions.

CAVEATS

The current PPI (v1.118) has a bug where $^ variables absorb following whitespace by mistake. This makes it harder to spot those as magic variables. Hopefully this will be fixed by PPI 1.200. In the meantime, we have a workaround in this module.

Additionally, PPI v1.118 fails to recognize %! and %^H as magic variables. PPI instead sees the ``%'' as a modulus operator. We have no workaround for that bug right now.

CREDITS

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

AUTHOR

Chris Dolan <cdolan@cpan.org>

COPYRIGHT

Copyright (c) 2007-2009 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.