Comment by ChuckMcM

4chan discussion aside, the concept here is that you 'sleep' n units of time for each element, where n is linearly related to the lexical relationship of the element to the other elements in the list. The 'aha' was that the resulting threads will 'wake up' or 'return' in lexical order.

Basically if you transform set L into the time domain, when collecting it back you get it back sorted.

Its a fun result, and as an exercise in systems analysis it can be enlightening to look at the impact of timer resolution, thread creation, and ordering, but ultimately the 'trick' is that you've exploited the 'insertion sort' that the kernel does on sleep events. You could try its close cousin "priority sort" where you create threads where you set the priority of each to be related to the value 'n' of the element, and all fractionally lower than the parent thread (most UNIXes are not that flexible but some realtime OSes are) then as the last step you 'yield' and the threads print out their contents in priority order and poof they are sorted. But again, the sorting happened in the kernel when they got inserted into the runq in priority order.