Since you're on Windows and it sounds like you have Excel installed, I'd suggest spending some time learning how to use Win32::OLE to directly control Excel via OLE. Once you get the hang of it, data retrieval from cells as well as writing data/formulas to cells become very easy. You'll want to use the OLE browser that comes with the Win32::OLE module. Also, you can record a macros and then look at it's source code to help figure out how to do more complicated tasks, such as graph creation/manipulation. Of course, both methods are giving you information in VB, which you'll need to convert to Perl. Also, you'll want to be doing some error trapping to help avoid creating orphaned Excel processes.

After doing a quick search on "win32 ole excel", there appears to be a number of perlmonks.org nodes covering using Win32::OLE to control Excel. That might be a good start with learning about that.