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Perl::Critic::PPerl::CUsercContributedaPerlADocumentation::ConstantBeforeLt(3)

NAME
       Perl::Critic::Policy::ValuesAndExpressions::ConstantBeforeLt - disallow
       bareword	before <

DESCRIPTION
       This policy is part of the "Perl::Critic::Pulp" add-on.	It prohibits a
       bareword	before a "<" to	keep you out of	trouble	with autoloaded	or
       unprototyped constant subs since	a "<" in that case is interpreted as
       the start of a "<..>" glob or readline instead of a less-than.  This
       policy is under the "bugs" theme	(see "POLICY THEMES" in	Perl::Critic).

	   use POSIX;
	   DBL_MANT_DIG	< 32   # bad, perl 5.8 thinks <>

	   func	<*.c>	       # ok, actual glob
	   time	< 2e9	       # ok, builtins parse ok

	   use constant	FOO => 16;
	   FOO < 32	       # ok, your own const

	   sub BAR () {	64 }
	   BAR < 32	       # ok, your own prototyped sub

       The fix for something like "DBL_MANT_DIG	< 10" is parens	either around
       or after, like

	   (DBL_MANT_DIG) < 10	# ok
	   DBL_MANT_DIG() < 10	# ok

       whichever you think is less worse.  The latter emphasises it's really a
       sub.

       The key is whether the constant sub in question is defined and has a
       prototype at the	time the code is compiled.  ConstantBeforeLt makes the
       pessimistic assumption that anything except "use	constant" and
       prototyped subs in your own file	shouldn't be relied on.

       In practice the most likely problems are	with the "POSIX" module
       constants of Perl 5.8.x and earlier, since they were unprototyped.  The
       default code generated by "h2xs"	(as of Perl 5.10.0) is similar
       autoloaded unprototyped constants so modules using the bare output of
       that suffer too.

       If you're confident the modules you use don't play tricks with their
       constants (including only using POSIX on	Perl 5.10.0 or higher) then
       you might find ConstantBeforeLt too pessimistic.	 It normally triggers
       rather rarely anyway, but you can always	disable	it altogether in your
       .perlcriticrc file (see "CONFIGURATION" in Perl::Critic),

	   [-ValuesAndExpressions::ConstantBeforeLt]

OTHER NOTES
       Bareword	file handles might be misinterpreted by	this policy as
       constants, but in practice "<" doesn't get used with anything taking a
       bare filehandle.

       A constant used before it's defined, like

	   if (FOO < 123) { ...	}   # bad
	   ...
	   use constant	FOO => 456;

       is reported by ConstantBeforeLt since it	might be an imported constant
       sub, even if it's much more likely to be	a simple mis-ordering, which
       "use strict" picks up anyway when it runs.

SEE ALSO
       Perl::Critic::Pulp, Perl::Critic

HOME PAGE
       http://user42.tuxfamily.org/perl-critic-pulp/index.html

COPYRIGHT
       Copyright 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017
       Kevin Ryde

       Perl-Critic-Pulp	is free	software; you can redistribute it and/or
       modify it under the terms of the	GNU General Public License as
       published by the	Free Software Foundation; either version 3, or (at
       your option) any	later version.

       Perl-Critic-Pulp	is distributed in the hope that	it will	be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A	PARTICULAR PURPOSE.  See the GNU
       General Public License for more details.

       You should have received	a copy of the GNU General Public License along
       with Perl-Critic-Pulp.  If not, see <http://www.gnu.org/licenses/>.

perl v5.24.1   Perl::Critic::Policy::ValuesAndExpressions::ConstantBeforeLt(3)

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