The bug reported in #75896: Cookie Expiry Date not set for "remember" session is quite interesting. Apparently Plack::Middleware::Session sends the session cookie on each request and if you don't set Expiry Date each time it will happily unset it.
I am thinking about changing the name to WebPrototypes::LoginForm. Some people did not like the name Plack::Middleware::Auth::Form from the start, because it is a bit more high-level then the other Auth middlewares, and now I have two more elements for quick web application prototyping under the WebPrototypes namespace.