How to create or modify an Excel file with embedded charts w/o Win32::OLE?

I am creating a web application that creates custom excel workbooks
containing embedded charts for users to download. I know Win32::OLE can
do this easily, but I'm guessing that if a lot of users try to use the
application at the same time it's going to cause huge performance problems.

I've looked at WriteExcel, but unfortunately it doesn't support embedded
charts. I've also looked at using SaveParser to modify a workbook with
pre-created charts, but it seems to remove all charts from the workbook.

Are there any other options out there?