This CGI::Application plugin allows to add custom throttling rules to you application. Having implemented it now, it seems easy to use, flexible, and well documented.
My one complaint is that it lacks a "singleton mode" like the ::TT plugin for CGI::Application has. Currently, there are several methods that need to be called on each request to configure the plugin. A singleton feature would allow details to be configured once at server start time, requiring less time during each request. ( That said, I have no indication that current design presents a performance bottleneck. )