in reply to CGI::Application::Plugin::Session (Why does CPAN hate me?)

Notice that the error actually occurs in CGI::Session, not CGI::Application::Plugin::Session. What you are seeing is a bug was introduced into CGI::Session in the latest release (v4.10). This was just reported on the mailing list a few hours ago.

There should be a new version out real soon, but in the mean time, you can downgrade your version of CGI::Session to an older version, and things should start to work.