The system I run this on is WinXP

Don't expect fork() and exec() on Windows to behave like they do on Unix-like systems. Windows has neither a fork() nor an exec() system call.

Perl has a rather thin emulation layer that fakes fork() and exec() well enough (using separate interpreter threads inside the same process) for some common cases. But the emulation is far from being perfect.

Cygwin has a different approach, it emulates fork() using mutexes and shared memory across different processes, which is quite slow. And even cygwin can't emulate exec().

Alexander