That's the response im getting back from the webservice

No, that's the status code of the response. I showed you (twice!) how to print the response.

The Data::Dumper output isn't as readable as ->as_string, but it also holds the info I was seeking:

'www-authenticate' => [
                        'Negotiate',
                        'NTLM'
                      ],
[download]

LWP only supports basic and digest authentication, but the server is asking for NTLM authentication. I'd start by checking out the module the Anonymous Monk mentioned.