It sounds like you are using something DOS, Windows 95, Windows 98 or Windows ME. You can't run scripts just by typing their name - you have to pass the script file name into perl first. This looks something like C:\SRC> perl myscript.pl add 1 2. I think you're typing something like C:\SRC> myscript.pl add 1 2 instead. Or at least that's what I get from your error message.