This is PSGI, Perl Web Server Gateway Interface -- ala Python's WSGI and Ruby's Rack. [PSGI protocol specification](http://github.com/miyagawa/psgi-specs/blob/master/PSGI.pod) is currently in draft. We're reviewing feedbacks before making it final. See also [FAQ](http://github.com/miyagawa/psgi-specs/blob/master/FAQ.pod) See [PSGI/Plack website](http://plackperl.org/) for more links.