Actually, I know (and knew) about this and thought about it while writing my reply; but I was talking about threads in the general sense, not the threading model found in Perl 5.6+. For all intents and purposes, "threads" in 5.6+ are userland forks. So in Perl I have the choice between kernel forks and userland forks (whose performance and memory use is as is to be expected - just what kernel forks used to be once upon a time) - now guess which ones I'll prefer. At least on sane OSes where kernel forks are available..