One important feature that exists in Pod::Parser that doesn't in Pod::Simple is an easy way to filter its output by section. While this can be implemented by a specific formatter, that isn't great. When Pod::Usage was ported to Pod::Simple, it added a rudimentary filter mechanism for its own output, but that isn't reusable.
I've written an implementation of this for Pod::Simple: https://github.com/perl-pod/pod-simple/pull/154. This is meant to be usable by all subclasses without any extra work. It is a bit invasive, as it changes when the _handle_element_start, _handle_element_end, and _handle_text methods are called. And I'm not certain about the interface for setting up filters. I wanted at least to be able to support Pod::Select filters unchanged, but it doesn't need to be limited to that. I would appreciate any feedback.
