CGI Scripts are really just HTML files with a .CGI extension, and any '?nn' occurances are expanded ( and can be formatted ) to whatever data the PNS holds for the referenced variables. The NET001.PDF is the best place to start.
You can use '?nn' references as arguments to JavaScript functions, so you can do further processing on that data within the browser once the page has been downloaded.
Because Perl is 'server-side scripting', it can't be executed on the PNS itself, but a returned page could probably be used to invoke a script which is served from another non-PNS server.