__END__

$VAR1 = {
          'TAGT' => {
                      'I1' => 1,
                      'I3' => 1
                    },
          'TTTT' => {
                      'I1' => 2, #From TTAT and TTT in I1, 
                                 #because their HD <= $d
                      'I2' => 1,
                    },
          'TTAT' => {
                      'I2' => 1,
                      'I1' => 2  # also From TTAT and TTT in I1
                    }
        };