I have implemented xAuth in Perl Net::Twitter, but it is currently untested. I am waiting approval of an xAuth access request for one of my own OAuth apps so I can test it.
I shipped a developer release to CPAN. It should be available, soon . If you're a perl dev and have xAuth access for your application, please download and test the developer release and give me some feedback. The documentation  indicates xAuth will return a 403 if the application hasn't been authorized. I'm getting a 401. Net::Twitter bug? Twitter bug? Twitter doc bug?  http://search.cpan.org/~mmims/Net-Twitter-3.11006_01/  http://apiwiki.twitter.com/Twitter-REST-API-Method:-oauth-access_token-for-xAuth @semifor