Perl::Critic::Policy::Variables::ProhibitPunctuationVars - Write C<$EVAL_ERROR> instead of C<$@>. |
Perl::Critic::Policy::Variables::ProhibitPunctuationVars - Write $EVAL_ERROR
instead of $@
.
This Policy is part of the core Perl::Critic distribution.
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
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.
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, $"
is known to cause difficulties
in interpolated strings.
ProhibitPunctuationVars relies exclusively on PPI to find
punctuation variables in code, but does all the parsing itself for
interpolated strings. When, at some point, this functionality is
transferred to PPI, ProhibitPunctuationVars will cease doing the
interpolating and the string_mode
option will go away.
Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>
Copyright (c) 2005-2011 Imaginative Software Systems. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module.
Perl::Critic::Policy::Variables::ProhibitPunctuationVars - Write C<$EVAL_ERROR> instead of C<$@>. |