use String::LCSS_XS qw[ lcss ];;

$a=''; $a .= chr 1<<$_ for 0 .. 63;;

print lcss( substr( $a, 10, 10 ), $a );;
ðÇÓáÇßÇÇÔÇÇõÇÇÞÇÇ­ÉÇÇ­áÇDZÇÇÇ&#8215;ÇÇÇ 0 13