This isn't intended as an insult or anything, I just want you to get the best help in the most efficient way:

This question is quite thoroughly answered in the documentation shipped with perl. I suggest you take a look at perldoc -f system (try man perlfunc on a Debian system without perldoc) for starters. This documentation is also available online at system.

Usually, the first place to look for info is perltoc which is a huge table of contents for things in the perl documentation. This has links to the perl FAQs, which are a fairly helpful resource as well.