my $matched = ( 'GCGAT' ^ 'GNGAT' ) =~ tr[\0][\0];

##</code><code>##

$xord = 'GCGAT' ^ 'GNGAT';;

print unpack 'C*', $xord;;
0 13 0 0 0

##</code><code>##

$matched = ( 'GCGAT' ^ 'GNGAT' ) =~ tr[\0][\0];;

print $matched;;
4

##</code><code>##

if(  $matched >= ( length( $q ) -1 ) ) {
    ## we have a winner