Hi, I am a Linux user and have not worked much on Windows but I have worked on similar project. There is a module "Unix::PID" on CPAN. if($pid->is_pid_running($$)) Before you start with your actual program you can check whether the a program of similar script/program name is running. If yes then exit else continue. So you kill a process by terminating itself. No explicit copmmand is used. I know this is not the ideal soltion but am sure there must be some module in windows too. Yograj.