So it sounds like you are saying there is no way to do it inside perl; I'll have to go to an external program. I didn't find anything named kill(\.exe)? on my XP box. A little research indicates that this was a tool that came with WIn2k, but not more recent OSs. I did find someone who had taken the code for that kill and updated to work with XP and to handle process trees. That's here
I'm still kind of hoping there's a good Perl solution out there so I don't have to be starting up external processes in a SIGINT handler. I took a second look at Proc::Killfam just in case it might work under Windows even if it isn't available via ppm. There seems to be some Cygwin compatibility in Proc::ProcessTable (which Proc::Killfam uses to figure out what processes need to be killed), but I don't know if that translates into Windows compatibility for P::K. I'm thinking not.
"If God had meant for us to think for ourselves he would have given us brains. Oh, wait..."