the ISP should give some type of prompt after your password has been sent and verified, try using minicom or the like to dial in manually and see what the prompt is if not ">". You could always just comment the "if($in =~ $pppprompt) {" and closing brace and see what happens, although if you do decide to do that, I'd suggest you put a small sleep in between the sending of the password and the $pppon.