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Perl::Critic::Policy::ControlSPerl::Critic::Policy::ControlStructures::ProhibitPostfixControls(3)

NAME
       Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls - Write "if($condition){
       do_something() }" instead of "do_something() if $condition".

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

DESCRIPTION
       Conway discourages using postfix control structures ("if", "for", "unless", "until",
       "when", "while") because they hide control flow.  The "unless" and "until" controls are
       particularly evil because they lead to double-negatives that are hard to comprehend.  The
       only tolerable usage of a postfix "if"/"when" is when it follows a loop break such as
       "last", "next", "redo", or "continue".

	   do_something() if $condition;	   # not ok
	   if ($condition) { do_something() }	   # ok

	   do_something() while $condition;	   # not ok
	   while ($condition) { do_something() }   # ok

	   do_something() unless $condition;	   # not ok
	   do_something() unless ! $condition;	   # really bad
	   if (! $condition) { do_something() }    # ok

	   do_something() until $condition;	   # not ok
	   do_something() until ! $condition;	   # really bad
	   while (! $condition) { do_something() } # ok

	   do_something($_) for @list;		   # not ok

	   LOOP:
	   for my $n (0..100) {
	       next if $condition;		   # ok
	       last LOOP if $other_condition;	   # also ok

	       next when m< 0 \z >xms;		   # fine too
	   }

CONFIGURATION
       A set of constructs to be ignored by this policy can specified by giving a value for
       'allow' of a string of space-delimited keywords: "if", "for", "unless", "until", "when",
       and/or "while".	An example of specifying allowed flow-control structures in a
       .perlcriticrc file:

	   [ControlStructures::ProhibitPostfixControls]
	   allow = for if until

       By default, all postfix control keywords are prohibited.

       The set of flow-control functions that are exempt from the restriction can also be
       configured with the 'flowcontrol' directive in your .perlcriticrc file:

	   [ControlStructures::ProhibitPostfixControls]
	   flowcontrol = warn die carp croak cluck confess goto exit

       This is useful if you're using additional modules that add things like "assert" or
       "throw".

NOTES
       The "die", "croak", and "confess" functions are frequently used as flow-controls just like
       "next" or "last".  So this Policy does permit you to use a postfix "if" when the statement
       begins with one of those functions.  It is also pretty common to use "warn", "carp", and
       "cluck" with a postfix "if", so those are allowed too.

       The "when" keyword was added to the language after Perl Best Practices was written.  This
       policy treats "when" the same way it does "if", i.e. it's allowed after flow-control
       constructs.  Thanks to brian d foy for the inspiration
       <http://www.effectiveperlprogramming.com/blog/543>.

BUGS
       Look for the "do {} while" case and change the explanation to point to page 123 when it is
       found.  RT #37905.

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.

perl v5.16.3		      Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls(3)
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