I'm no expert, but fork and perlfork talk at length about not to use kill on children when fork was emulated.

See https://perldoc.perl.org/perlfork#kill()

There are various alternatives listed in perlipc though.

An SSCCE with tests might help provide alternatives.

> If I just use Win32::Process, then this would be a dependency also on Linux

I'm quite sure that you can have install dependencies based on the actual OS. Never tried this tho.

HTH. :)