G'day swl,

See "Re^7: How can I do a numeric sort on a substring? [Benchmark: reworked and extended]". I've added sort_key_integer and sort_key_natural (made some guesses about the code) as well as a couple of additions of my own.

"It would be interesting to know how the Sort::Key approaches go under a more recent Perl."

I'm not seeing a huge difference between your output and my latest. SKn is at the slow end of the spectrum; SKi is by far the fastest (substantially faster on my system with Perl 5.34.0).