I am doing a lot of stuff with E-Mails we get from customers and suppliers. My preferred way is the way you mentioned, doing some filtering based on subject and sender, then access the mails with Net::IMAP::Simple and then deleting them or putting them into a subfolder ./archiv or ./done. In most cases I store the data in a database table which makes sense when it comes to evaluating the data in my opinion.

If you want / need Excel files you could use Excel::Writer::XLSX in addition to create Spreadsheets based on your database.