It runs atop the Plack framework, but since it really handles the whole HTTP transaction, it is not appropriate to use most middleware modules. (NOTE: I will write more about this in the future.)
This module is extremely young and it is a port of an pretty young (June 2011) module in another language (ruby), which itself is a port of a still kind of young module (March 2009) in yet another language (erlang). But that all said, it really seems like a sane idea and so I stole it and ported it to Perl.
NOTE: More details to come, but for now, this is all.