my $indexfile = {
                         'GCTCAGGA' => '4',
                         'AGCGTAGC' => '5',
                         'TTCTGCCT' => '3',
                         'CATGCCTA' => '6',
                         'TCGCCTTA' => '1',
                         'GTAGAGAG' => '7',
                         'GCGTAAGA' => '13',
                         'TAGATCGC' => '9',
                         'CTAGTACG' => '2',
                         'CTAAGCCT' => '16',
                         'CTCTCTAT' => '10',
                         'ACTGCATA' => '14',
                         'AGAGTAGA' => '12',
                         'TATCCTCT' => '11',
                         'AAGGAGTA' => '15',
                         'CCTCTCTG' => '8'
                       };