The 'next if..' line in this post, and the 'unless ...' clause in the next post are unneccessary, and slow the algorithm down for an array of ~20 elements or larger.

This is because if you assume the cost of a comparison is 1, and the cost of a swap is ~10, then when $i > 10, the savings on a swap are lost because odds are < 1 in 10 that you're swapping the same element. Benchmark comparison against swapping, and do the math. YMMV.