To add to what Corion said, Windows doesn't have signals. Anything you see in Perl is an emulation. As with almost all emulations, there are flaws and limitations. Windows is based around messages sent to windows (due to its origins as a windowing environment running over DOS).

That means you'll probably have better luck by using Windows calls directly. WaitForSingleObject and family allows you to wait for child processes to die by waiting on a process handle. This is can be obtained when creating the child and by other means. It supports a timeout.