Or, use the cygwin version of perl on Windows, which does support fork

I usually prefer separate code paths for Unix vs Windows code that manipulates processes. One example that springs to mind is Re: How to portably stop processes? (Timing out Commands on Unix and Windows and Win32:: References), with links to sample code to create, time, and kill processes on Unix (via fork, exec, kill, waitpid) and Windows (via Win32::Job).

Unfortunately, we have no information on the OP's environment and the specific problem/s that need to be solved (and why the OP feels that Parallel::ForkManager is the best way to solve them) ... and, sadly, it's looking increasingly likely that we won't hear from the OP again in this thread.

👁️🍾👍🦟