use strict;
use warnings;

my $one  = "AGCTGATCGAGCTAGTACCCTAGCTC";
my $two  = "AGATGATCGAGCTAGTACCCTATCTC";
# Diffs here  ^                   ^

my $diff = $one ^ $two;

my @posns = ();

push @posns, pos $diff while $diff =~ m{[^\0]}g;
print qq{Differences, 1-based counting, at - @posns\n};

@posns = ();

push @posns, pos $diff while $diff =~ m{(?=[^\0])}g;
print qq{Differences, 0-based counting, at - @posns\n};