The POD for CGI.pm has a pretty good description of handling file uploads. Be sure to read it (and use CGI;). To that I might add that you need to be conscious of security concerns. Ovid's Online CGI Course (free) does a pretty good job of getting your feet wet in the area of starting to understand security issues.

I personally like the Mouse Book (CGI Programming with Perl, from O'Reilly & Associates). It has a great description of how to handle file uploads, and goes to the trouble of explaining how to deal with keeping the process relatively secure. You may find a copy in the library, but if you do much with CGI, it's a good resource to have on your own bookshelf.

I hope this helps...