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.IX Title "Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls 3pm"
.TH Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls 3pm 2023-07-26 "perl v5.38.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls \- Write "if($condition){ do_something() }" instead of "do_something() if $condition".
.SH AFFILIATION
.IX Header "AFFILIATION"
This Policy is part of the core Perl::Critic
distribution.
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Conway discourages using postfix control structures (\f(CW\*(C`if\*(C'\fR, \f(CW\*(C`for\*(C'\fR,
\&\f(CW\*(C`unless\*(C'\fR, \f(CW\*(C`until\*(C'\fR, \f(CW\*(C`when\*(C'\fR, \f(CW\*(C`while\*(C'\fR) because they hide control
flow.  The \f(CW\*(C`unless\*(C'\fR and \f(CW\*(C`until\*(C'\fR controls are particularly evil
because they lead to double-negatives that are hard to comprehend.
The only tolerable usage of a postfix \f(CW\*(C`if\*(C'\fR/\f(CW\*(C`when\*(C'\fR is when it follows
a loop break such as \f(CW\*(C`last\*(C'\fR, \f(CW\*(C`next\*(C'\fR, \f(CW\*(C`redo\*(C'\fR, or \f(CW\*(C`continue\*(C'\fR.
.PP
.Vb 2
\&    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 \ez >xms;             # fine too
\&    }
.Ve
.SH CONFIGURATION
.IX Header "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:
\&\f(CW\*(C`if\*(C'\fR, \f(CW\*(C`for\*(C'\fR, \f(CW\*(C`unless\*(C'\fR, \f(CW\*(C`until\*(C'\fR, \f(CW\*(C`when\*(C'\fR, and/or \f(CW\*(C`while\*(C'\fR.  An
example of specifying allowed flow-control structures in a
\&\fI.perlcriticrc\fR file:
.PP
.Vb 2
\&    [ControlStructures::ProhibitPostfixControls]
\&    allow = for if until
.Ve
.PP
By default, all postfix control keywords are prohibited.
.PP
The set of flow-control functions that are exempt from the restriction
can also be configured with the 'flowcontrol' directive in your
\&\fI.perlcriticrc\fR file:
.PP
.Vb 2
\&    [ControlStructures::ProhibitPostfixControls]
\&    flowcontrol = warn die carp croak cluck confess goto exit
.Ve
.PP
This is useful if you're using additional modules that add things like
\&\f(CW\*(C`assert\*(C'\fR or \f(CW\*(C`throw\*(C'\fR.
.SH NOTES
.IX Header "NOTES"
The \f(CW\*(C`die\*(C'\fR, \f(CW\*(C`croak\*(C'\fR, and \f(CW\*(C`confess\*(C'\fR functions are frequently used as
flow-controls just like \f(CW\*(C`next\*(C'\fR or \f(CW\*(C`last\*(C'\fR.  So this Policy does
permit you to use a postfix \f(CW\*(C`if\*(C'\fR when the statement begins with one
of those functions.  It is also pretty common to use \f(CW\*(C`warn\*(C'\fR, \f(CW\*(C`carp\*(C'\fR,
and \f(CW\*(C`cluck\*(C'\fR with a postfix \f(CW\*(C`if\*(C'\fR, so those are allowed too.
.PP
The \f(CW\*(C`when\*(C'\fR keyword was added to the language after Perl Best
Practices was written.  This policy treats \f(CW\*(C`when\*(C'\fR the same way it
does \f(CW\*(C`if\*(C'\fR, i.e. it's allowed after flow-control constructs.  Thanks
to brian d foy for the
inspiration <http://www.effectiveperlprogramming.com/blog/543>.
.SH BUGS
.IX Header "BUGS"
Look for the \f(CW\*(C`do {} while\*(C'\fR case and change the explanation to point
to page 123 when it is found.  RT #37905.
.SH AUTHOR
.IX Header "AUTHOR"
Jeffrey Ryan Thalhammer <jeff@imaginative\-software.com>
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (c) 2005\-2011 Imaginative Software Systems.  All rights reserved.
.PP
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.