>perl -wMstrict -lE
"my $s1 = 'abcdefg';
 my $s2 = 'abcdefg';
 ;;
 my $t = $s1 ^ $s2;
 ;;
 my ($f) = $t =~ /^(\x{00}*)/;
 say length $f;
 ;;
 $t =~ /^\0*/ && say $+[0];
"
7
7