I think you should change the order of operations:

1. Extracts the page content using LWP::UserAgent, HTML::TableExtract
2. Creates the Excel using Spreadsheet::WriteExcel
3. Writes to the excel and closes it
4. Lets the user download it

This way you would avoid creating the Excel file if the content recovered is not correct (think getting a 404 from LWP).

I would also consider two things:

• Use XML instead of creating a Excel file: unless your formating and using formulas in the Excel, XML is more portable and probably faster to write using XML::Writer. Newer versions of Excel can work pretty well with XML (unless the XML content is really large).
• If you really need Excel, then assign the content of the file to a scalar instead of an array. If you are at a Windows OS, maybe you should use binmode() before printing it.