This is great stuff, but I think you're a bit confused about the namespaces i've chosen (unless i've got typos somewhere, though i did run a grep on the directory, so i don't think so).

The two main namespaces I'm using are Application::Pipeline and WWW::Pipeline, where the latter is a subclass with phases that suit HTTP request processing.

Obviously while i thought long and hard about the plugin/services bit, and tried to match what a lot of people were asking for on the mailing list, i didn't do much research on what is already out there. I'll take a look around.