Thanks for this. You've found two problems, one of which I had already discovered and solved, the other I had not.

The first was that this code

        if( @seq > 1 and $seq[ -1 ][ 0 ] > ( $seq[ -2 ][ 0 ] + 1 ) ) {
            pop @seq;
            if( @seq >= 4 ) {
                push @seqs, [ @seq ];
            }
            undef @seq;
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discarded the non sequential value. If that was the start of a new sequence, the new sequence was missed or truncated. The fix is:

        if( @seq > 1 and $seq[ -1 ][ 0 ] > ( $seq[ -2 ][ 0 ] + 1 ) ) {
            my $temp = pop @seq;
            if( @seq >= 4 ) {
                push @seqs, [ @seq ];
            }
            @seq = $temp;
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The second is that if the last value of the set is also the last value of a sequence, and that sequence is also the minimal length (4 in this case), that sequence is not saved. I'm not sure how to fix this yet.

Update: Not as clean as I would hope to achieve, but a final check for a complient sequence outside the while loop fixes the second problem. I'll update the code above to reflect the fix.