use if eval { require mod; 1 }, qw' constant haveMod 1 ';
use if not exist $INC{'mod.pm'}, qw' constant haveMod 0 ';
use Module::Loaded qw' is_loaded ';
use constant haveMod => !! is_loaded('mod');

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In reply to Re: constants wont optimize by Anonymous Monk
in thread constants wont optimize by patcat88

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