This is the title of a blog post by Misko Hevery. There are also lot's of other materials authored by him freely available on the net. I have just started exploring them, and there is a lot of repetition if you just google around like me - but I already want to recommend it to anyone working on improving the design of their programs.
WebNano does not (yet?) meet all the design criteria he is talking about - but he is putting into words many of the foggy intuitions that made me not satisfied with all of the existing Perl web framework and write yet another one.