Some time ago I needed NTLM authentication, and tried the modules available from CPAN. There are two Authen::NTLM modules, one from Yee Man Chan and another from David Bussenschutt. While trying to use these on live servers, I found that (in my case at least) the former didn't work, but the latter did. Also, by that time both modules were 5 years unmaintained, but I tried to work out patches for both, and surprisingly David answered and incorporated my patches.

Also, there's LWP::Authen::Ntlm which I didn't use, but I tried it and it works too (being based on David's code). I'm unsure if you really want to use Authen::NTLM::HTTP in view of these alternatives, but if you really do, I'd love to see it completely rewritten and using David's Authen::NTLM module as the base.