There used to be a fantastic page up at Mr. Peabody explains fork(), explaining how fork() works on Unix, and how the fork() emulation in Perl for Win32, 5.6 and higher, works. You may still be able to find it at the Wayback Machine — it currently (still) works, but who knows for how long: I have the impression archive.org no longer adds new pages.
in reply to What is the difference between Windows fork an Unix fork ?
For posteriority, I made a copy available at http://users.pandora.be/bartl/classicperl/fork/all.html. Some images are missing, they're not at the Wayback Machine either. I have reconstructed some.
What's worse: it looks like some images have started to disappear from archive.org. Seems like I was just in time to rescue most.