Google::SAML::Response can be used to generate a signed XML document
that is needed for logging your users into Google using SSO.

You have some sort of web application that can identify and
authenticate users. You want users to be able to use some sort of
Google service such as Google mail.

When using SSO with your Google partner account, your users will send
a request to a Google URL. If the user isn't already logged in to
Google, Google will redirect him to a URL that you can define. Behind
this URL, you need to have a script that authenticates users in your
original framework and generates a SAML response for Google that you
send back to the user whose browser will then submit it back to
Google. If everything works, users will then be logged into their
Google account and they don't even have to know their usernames or
passwords.

WWW:	http://search.cpan.org/dist/Google-SAML-Response/