#!/usr/bin/perl

use strict; # https://www.perlmonks.org/?node_id=11155923
use warnings;
use feature 'bitwise';

my $str1='LFGSLSIIVAHHM';
my $str2='LFGSLSIIVSHHM';

print +($str1 ^. $str2) =~ tr/\0//, " characters are the same\n";
[download]

Outputs:

12 characters are the same
[download]