The documentation states:

"However, you can only rewrite the features that Spreadsheet::WriteExcel supports so macros, graphs and some other features in the original Excel file will be lost. Also, formulas aren't rewritten, only the result of a formula is written."

And later:

"If there is some feature of an Excel file that you really, really need then you should use Win32::OLE with Excel on Windows. If you are on Unix you could consider connecting to a Windows server via Docserver or SOAP, see Writing Excel Files."