What does this sound like to me? Duo-Authentication is a new thing connoting dual-authentication, which can be achieved in a variety of ways. I identify Duo with the google toolchain, and it's just like them to lay claim to a semi-word.

Meanwhile, WWW::Mechanize is not new. It is not trimmed out for what the internet has become. What's more, your objective seems to be to bypass this authentication with cookies. Preventing you from what you're attempting is the raison d'etre for duo-authentication.

I don't know what all goes into a cookie, but it's not the data you need for the *next* duo-verification. You could put a lot of cases to rest by posting the URL you are trying to outwit.