( eval "( $string1 | $string2 )  =~  tr[$n1][$n1]" ),
            ( eval "( ~$string1 & $string2 ) =~ tr[\$ndiff][\$ndiff]" ),
            ( eval "( $string1 & ~$string2 ) =~ tr[\$ndiff][\$ndiff]" ),
            ( eval "( $string1 & $string2 )  =~ tr[$n2][$n2]" ) ),