foreach my $seq (keys %SEQ) {
            foreach my $codon (@codons) {
                $SEQ{$seq.$codon} = 1;
            }
            delete $SEQ{$seq};
        }    

##</code><code>##

        my @seq_keys = keys %SEQ;
        foreach my $seq_key_num (0..$#SEQ) {
            my $seq = $seq_keys[$seq_key_num];
            foreach my $codon (@codons) {
                $SEQ{$seq.$codon} = 1;
            }
            delete $SEQ{$seq};
        }