Since I wrote the post Net::Google::Analytics Extended Example Google updated the API and the Perl module was modifed to accomodate. That example is broken and I am providing an updated version here.
There are two major changes. First, Google started using OAuth2 for authentication so that code is different. There are plenty of details in the API docs.
Second, the Perl module has a bit smoother interface. I'm not sure if this was an API change or a module enhancement, I think the latter. In any case the new code is a lot cleaner.