>> All frameworks (ish) play nicely with Plack, which is a straight rip-off of Rack

When developing PSGI/Plack, Miyagawa not only looked at Rack but also WSGI (Python) and also the proposed improvements to WSGI.

ref: http://bulknews.typepad.com/blog/2009/09/psgi-perl-wsgi.html | http://www.b-list.org/weblog/2009/aug/10/wsgi/ | http://jacobian.org/writing/snakes-on-the-web/