Very interesting!

To be honest, I'm not really interested in space.
The tsv I'm playing with has about 500k lines, and I can already run my algorithm with everything in ram.

It's just that my naive implementation is slow, and I want to see how fast it can be. I know that I lost a lot of performance when I started comparing list of strings.
I just expect bit array to be much much faster where applicable. To confirm that, I'll be able to compare with other similar columns that cannot be turned into bit array.

Thank you for making me learn a bit more about Perl today.

edit:

To reproduce what you did for Jaccard module, calling set_to_string first, I also did the same for your implementation.
I makes sense in my actual context as I first read the whole file, cleaning rows, etc. so creating the bit array will be part of the process.

What's interesting is that it doubled the performance hash: 340k/s -> 420k/s, bits: 800k/s -> 1.7m/s
Also, using `my $ic = unpack '%b*', pack 'N', $int;` provides slightly better performance (+1% consistently) that your implementation with Hamming weighs.
Now, I need to read a bit about Hamming weighs. Working with bits is always interesting, but it feels kind of a cipher.