NAME¶
Perl::Critic::Policy::Variables::ProhibitPunctuationVars - Write
"$EVAL_ERROR" instead of "$@".
AFFILIATION¶
This Policy is part of the core Perl::Critic distribution.
DESCRIPTION¶
Perl's vocabulary of punctuation variables such as $!, $., and $^ are perhaps
the leading cause of its reputation as inscrutable line noise. The simple
alternative is to use the English module to give them clear names.
$| = undef; #not ok
use English qw(-no_match_vars);
local $OUTPUT_AUTOFLUSH = undef; #ok
CONFIGURATION¶
The scratch variables $_ and @_ are very common and are pretty well understood,
so they are exempt from this policy. The same goes for the
less-frequently-used default filehandle "_" used by
stat().
All the regexp capture variables ($1, $2, ...) are exempt too. $] is exempt
because there is no English equivalent and Module::CoreList is based upon it.
You can add more exceptions to your configuration. In your perlcriticrc file,
add a block like this:
[Variables::ProhibitPunctuationVars]
allow = $@ $!
The "allow" property should be a whitespace-delimited list of
punctuation variables.
Other configuration options control the parsing of interpolated strings in the
search for forbidden variables. They have no effect on detecting punctuation
variables outside of interpolated strings.
[Variables::ProhibitPunctuationVars]
string_mode = thorough
The option "string_mode" controls whether and how interpolated strings
are searched for punctuation variables. Setting "string_mode =
thorough", the default, checks for special cases that may look like
punctuation variables but aren't, for example $#foo, an array index count;
$$bar, a scalar dereference; or $::baz, a global symbol.
Setting "string_mode = disable" causes all interpolated strings to be
ignored entirely.
Setting "string_mode = simple" uses a simple regular expression to
find matches. In this mode, the magic variables $$, "$'", $# and $:
are ignored within interpolated strings due to the high risk of false
positives. Simple mode is retained from an earlier draft of the interpolated-
strings code. Its use is only recommended as a workaround if bugs appear in
thorough mode.
The "string_mode" option will go away when the parsing of interpolated
strings is implemented in PPI. See "CAVEATS" below.
BUGS¶
Punctuation variables that confuse PPI's document parsing may not be detected
correctly or at all, and may prevent detection of subsequent ones. In
particular, $" is known to cause difficulties in interpolated strings.
CAVEATS¶
ProhibitPunctuationVars relies exclusively on PPI to find punctuation variables
in code, but does all the parsing itself for interpolated strings. When, at
some point, this functionality is transferred to PPI, ProhibitPunctuationVars
will cease doing the interpolating and the "string_mode" option will
go away.
AUTHOR¶
Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>
COPYRIGHT¶
Copyright (c) 2005-2011 Imaginative Software Systems. All 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.