If deleting the temporary internet files is your only requirement, then there's no need to know the actual user list -- you can simply just find (File::Find) and delete c:\documents and settings\*\local settings\Temporary Internet Files\* or whatever the wildcard is.

To find the actual users, i'm not sure -- i find out how to do that in general first, and then use that as a guide to find the right Win32 module. (Or maybe it's an external command you can backtick)
Update: Doh -- i cpan-searched for "Win32::Admin" .. BrowserUK found the right one at Win32::NetAdmin .