#!/usr/bin/perl

my ($a, $b, $c) = qw (AAATGCCTT AAAAGCGTC AAAGGCGTC);
my ($similar, $dissimilar); 
for (0 .. length($a)-1) {
    if (substr($a,$_,1) eq substr($b, $_, 1) and substr($b, $_, 1) eq substr($c, $_, 1)) {
        print "MATCH";
        $similar ++;
    } else {
        print "NO MATCH";
        $dissimilar ++; 
    }
    print " at position $_\n";
}
print "There were " . $similar . " similar and " . $dissimilar . " dissimilar.\n";