So long as you run your script from an account which is authenticated to the domain, and has admin privledges to the remote system, nothing special is needed.

Just like it says in the docs:
Win32::StartService(hostname, servicename)

You may want to consider looking into the Windows Management Interface(WMI), it has a scripting API available to perl users. It too could be used to manage services on a remote systems(and lots more). Its kinda kludgy though, and involves more work than using Win32::Service. WMI is microsoft's version of the WBEM standard which came out of the DTMF. It'll hit prime time as windows2000 becomes more common.