# leading common substring
# returns length of LCS
# requires Perl 5.6+
sub lcs {
  ($_[0] ^ $_[1]) =~ /\0*/;
  return $+[0];
}

##</code><code>##

# leading common substring
# returns length of LCS
# requires Perl 5.6+
sub lcs {
  ($_[0] ^ $_[1]) =~ /(\0*)/;
  return length $1;
}