Excellent comments, BrowserUK.   Very informative.

My take on the matter is that, “if you are killing threads or processes, or giving up time slices, you’re going about it the wrong way.”   The timing of threads/processes is and must be completely unpredictable.   Furthermore, the things that they do are things that they need to be able to finish doing.   Instead of being “killed,” they should be “informed that it is now time for them to please roll over and die.”   Therefore, the consistently best and most-stable arrangement, I think, is to construct persistent threads (designed to handle many units of work in their lifetime), and to connect them with flexible hoses ... i.e. IPC queues.   Control the system with messages.   Indicate that it’s time to die with a shared flag, and also send a message to that effect so that any thread that’s listening on a queue will wake up, read it, put its own house in order, and die.   You can reliably implement this protocol on any system, using existing CPAN packages, thereby neatly eliding yourself out of the entire cross-platform question.   Somebody else has already done it for you.   Timing problems are eliminated by adopting a better and more rugged design.

“When faced with an edge-case, do the smart thing ... stay away from the edge.   Looks like it’s a long way down.”