"I want to add the capability of having the users upload a file from their local system to the server for conversion (limited by $maxsize, of course). The hitch here is that I need to provide a way for the users to be able to delete the file from the server after they've uploaded it.

Have you considered using webdav for uploading/deleting of files ?

Webdav is supported by Apache and IIS (among others) and allows clients to upload files, change or delete them. Internet explorer is a webdav client and works ok with Apache webdav, just do a File/open, indicate the webdav url and check "open as web folder".

After that, users can drag and drop files into that folder, as if it where a common folder.

You could even put perldav to god use :-)