use strict;
use warnings;
my (%hash, $value);

print "Without\n";

$hash{key} = $value;

if ($hash{key} == 42) {
  print "taking appropriate action\n"
}

print "With\n";

$hash{key} = $value || 0;

if ($hash{key} == 42) {
  print "taking appropriate action\n"
}