I don't know how, or even IF, this can be done yet. SharePoint is more dependent on Win32 and IE than almost anything I can think of. There are many features of SharePoint that require IE 6 or higher to use, such as viewing a list in tabular form and (IIRC) uploading multiple files.

That said, you may be able to use Win32::OLE to open and control an IExplorer object, especially if you are writing Excel files with Perl.

Let me know if this works so I can steal your technique. :-)