Quoting perlwin32: Signal handling may not behave as on Unix platforms (where it doesn't exactly "behave", either :). For instance, calling die() or exit() from signal handlers will cause an exception, since most implementations of signal() on Win32 are severely crippled. Thus, signals may work only for simple things like setting a flag variable in the handler. Using signals under this port should currently be considered unsupported.

The kill command does not really send a signal under Win32 but as on all systems, SIGKILL is not something you can catch and handle. Your process never really "sees" that signal, it just gets stopped and removed from the set of active processes.

Update: I just saw you're not sending a SIGKILL, so it seems that the signal emulation across processes on Win32 is just SIGKILL no matter what number you hand to kill.