in reply to NSI-style WHOIS Module?
From what I can see Net::XWhois is what you want, it allows you to specify a server to query. Net::Whois appears to use internic for its queries. Both modules are available on cpan. As far as your questions about the different servers, I couldn't tell you, I have no knowledge about them.
-- Can't never could do anything, so give me and inch, I'll make it a mile.