D'oh, that's the one thing I forgot. WWW::PAUSE::CleanUpHomeDir comes closest to what I need, with its cleanup() method. But anyway, in case anyone needs it, I've also written the JavaScript (tested in Opera). At least, using the browser + JavaScript you can double check visually before hitting Delete.

https://github.com/sharyanto/userjs/blob/master/pause-delete_files-select_all_older_releases_files.user.js

Thanks everybody.