This is a classic case for "what did you try?" ...and since you've been a Monk for some 5 years, you may even have heard that before. In fact, this is one of two posts today by you demonstrating a serious lack of effort. - -

And what did you search to learn the answer?

Obvious candidates (in no particular order):

1. Super Search
2. Tutorials
3. perldoc CGI
   ...and, of course,
4. big G (with 119k results for that search)