The thing with perl threads is that pretty much nobody uses them. They work fine, as far as I know, but with a default 16MB stack size and "share nothing" semantics don't start more than a few. Perl is more unix centric and people just prefer to fork and use the well baked IPC mechanisms. Various libraries such as POE make fork+IPC easy enough that it's hard to see the need for threads in the kinds of domains where a language like perl is applicable.