If all you're doing is reading data from the workbook, Win32::OLE may be a bit of overkill. You don't need all of the application control that it provides. Have you looked at the plethora of other excel modules available on cpan? Spreadsheet::ParseExcel would seem to be a candidate, if you can live with the limitations (no formula support).

Now, if you do in fact need the application control provided by Win32::OLE, then it sounds like you would want the read-only flag. Just closing without saving changes could leave you with problems if another user has the spreadsheet open. I don't know that off the top of my head, but I'll see if I can track it down.

Update: Spreadsheet::Read looks like an even better match.