sub interleave2 {
  my ($remaining_a, $remaining_b) = @_;
  if ($remaining_a > 1 && $remaining_b) {
    my $b_range = int($remaining_b/($remaining_a - 1));
    return 'A' . 'B' x $b_range . interleave2($remaining_a - 1, $remaining_b - $b_range);
  } elsif ($remaining_a) {
    return 'A' . interleave2($remaining_a - 1, $remaining_b);
  } elsif ($remaining_b) {
    return 'B' . interleave2($remaining_a, $remaining_b - 1);
  } else {
    return ''; # Just for completeness
  }
}