The screensaver information is stored in and around the HKEY_CURRENT_USER\Control Panel key in the registry. The information about which screensaver is used is under the \Desktop key and the individual settings for the screensavers appear to be in \Screen Saver.{name} keys, where name is the name of the screensaver.

In order to edit this information using Perl you will want to look at Win32::TieRegistry. This module can be used on local and remote registries if you have the correct access.

Note that the screensaver info is stored under the current user key so setting it remotely will require that you iterate through the users in the HKEY_USERS key.