compare string

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use open qw(:std :encoding(utf8));
use feature q(say);

sub Compare($$);
sub Rate($$);

my $s1 = 'あいう1';
my $s2 = 'あいえ23';
say Rate($s1, $s2) . '%';

sub Compare($$) {
  my ($s1, $s2) = @_;
  my $len1 = length $s1;
  for (my $i = $len1; $i > 0; --$i) {
    for (my $j = 0; $i + $j <= $len1; ++$j) {
      return $i if $s2 =~ substr $s1, $j, $i;
    }
  }
  return 0;
}
sub Rate($$) {
  my ($s1, $s2) = @_;
  return Compare($s1, $s2) * 100.0 / (length $s2);
}