#!perl
use strict;
use warnings;

my $difference = 1;
my @generations = ( 'TTTATTT', 'TTTTTTTT', 'TBTTTTT' );

my %mismatch;
my $times = $difference == 1 ? 'time' : 'times';
my $columns = $difference == 1 ? 'column: ' : "columns:\n";
my $length = length $generations[0];

for ( my $column = 0 ; $column < $length ; $column++ ) {
    for ( my $gen = 1 ; $gen < scalar @generations ; $gen++ ) {
        my $last = substr $generations[ $gen-1 ], $column, 1;
        my $current = substr $generations[ $gen ], $column, 1;
        push @{ $mismatch{ $gen } }, [ $column, $last, $current ] unless $last eq $current;
    }
}

my $out = '';
for my $mm ( sort keys %mismatch ) {
    if ( scalar @{ $mismatch{ $mm } } == $difference ) {
        $out .= sprintf "mismatched %d %s between gens %d and %d at %s",
            $difference, $times, $mm, $mm-1, $columns;
        foreach my $c_l_c ( @{ $mismatch{ $mm } } ) {
            $out .= sprintf " %d ( %s and %s ),\n",  @$c_l_c;
        }
        $out .= "\n";
    }
}

print $out;