The files in this directory are predefined grammars for different languages and contexts. They are intended to be used for common search patterns, and not intended to be complete PEG definitions of language grammars, other than bp.bp, which is included for stress-testing purposes, as well as a showcase of some BP features.
If you want to add your own grammar, the easiest way to do so is to create a
.bp file in ~/.config/bp/. The syntax for grammar files is fully and
formally defined in bp.bp, but in short, it's a list of
whitespace-separated rule definitions of the form id __ ":" __ pattern.