my $regex = qr/$string/;

while (my $word = <DICT>) {
   chomp($word);
   if ($word =~ $regex) {
      $yep++;
   }
}

##</code><code>##

while (my $word = <DICT>) {
   chomp($word);
   if ($word =~ /$string/o) {
      $yep++;
   }
}