in reply to Writing Excel spreadsheets with Perl
There is one advantage of Win32::OLE that has not been mentioned. It works with Excel 2007. This works because Win32::OLE makes use of the COM objects installed on the workstation itself. While this limits portability beyond Windows (and perhaps even on Windows for certain features), it has the advantage of not requiring an update to the module.
As far as I can tell, none of the Spreadsheet::<module> modules work with Excel 2007. Perhaps this can be addressed in a future build, but currently it is necessary to use Win32::OLE if you have to deal with the newer version.
The file format is different for Excel 2007 than for Excel 2003 and earlier. Microsoft even designated a new extension for it, *.xlsx (2007) instead of *.xls (2003 and earlier).