POE::Loop is a documentation for POE's event loop bridge interface.
POE's runtime kernel abstraction uses the "bridge" pattern to encapsulate services provided by different event loops. This abstraction allows POE to cooperate with several event loops and support new ones with a minimum amount of work.
POE relies on a relatively small number of event loop services: signal callbacks, time or alarm callbacks, and filehandle activity callbacks.
The rest of the bridge interface is administrative trivia such as initializing, executing, and finalizing event loop.
POE::Kernel uses POE::Loop classes internally as a result of detecting which event loop is loaded before POE is. You should almost never need to use a POE::Loop class directly, although there is some early support for doing so in cases where it's absolutely necessary.
See "Using POE with Other Event Loops" in POE::Kernel for details about actually using POE with other event loops.