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 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.
This Policy is not configurable except for the standard options.
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.
Initial development of this policy was supported by a grant from the Perl Foundation.
Chris Dolan <cdolan@cpan.org>
Copyright (c) 2007-2008 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.