ikegami pointed out your errors. Here are some more tips/links:

• Read Writeup Formatting Tips. And before you post, hit the 'Preview' button.
• use strict and warnings
• Use $! with die, instead of "$ !".
• Use print instead of printf ...

Don't fall into the trap of using a "printf" when a simple "print" would do. The "print" is more efficient and less error prone.

I also noticed you are opening the same filename $ARGV[0] for both input and output. You probably don't want to do that.