I've tackled this task several ways including sending a csv file and building an excel file with SpreadSheet::WriteExcel

My favourite trick for delivering dynamically generated Excel spreadsheets over the web is this:
Send an html file to the browser with the Content-type header set to the MIME type for Excel (application/msexcel).

The browser should prompt the user to open the file in Excel. Excel will parse and display the contents of the file, in cells so if your page is a bunch of tables, Excel will create a 1-to-1 cell mapping for the HTML table cells to Excel cells. You can make the tables as complex as you like, style them and the information and formatting comes through. It's a very fast way to get up and running especially if you are using a templating system like Template-Toolkit, HTML::Template or Petal.

This has worked since the version of Excel before Office XP (2003)