It is not an easy problem in the general case

I implemented in C a system with time-out and a command ish wich I use in production. It has one limitation and there is a trick: I use setpgid() in the father and the child (you need both to avoid a race condition), this way I can kill(pgid), which actually kills everything the exec()ed process starts ...except if it itself uses setpgid() like daemons (this is the limitation ;)</>

using the POSIX module, I think a pure perl solution is not too complicated (a line by line translation, but hey if it works...) if you want the code contact me at sgt19DELETE@tidALLCAPS.es