use strict;
use warnings;

my $string = 'ATATGCGCAT';

for my $num (0 .. 2**11 - 1) {
  print "$num: ",
    join('',
      map { substr($string, $_, 1) . ($num & (2**(9 - $_)) ? '2' : '1'); }
      0 .. 9
    ), "\n";
}