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, 2019, 2021 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 v5.32.1                                       2021-02-28             Perl::Critic::P...onstantBeforeLt(3pm)