I was working on a similar script recently and found a very good example at this site:

http://www.webmasterbase.com/article/474

This web page shows an example of how to upload a file, including both the html code as well as perl code. As you can see, the perl script is very similar to the one suggested by PerpLexicon, but there is some extra information and an explanation which I found helpful.

I hope this helps!