This module provides some XS functions to assist in writing parsers for
'sub'-like syntax, primarily for authors of keyword plugins using the
'PL_keyword_plugin' hook mechanism. It is unlikely to be of much use to
anyone else; and highly unlikely to be any use when writing perl code using
these. Unless you are writing a keyword plugin using XS, this module is not
for you.

This module is also currently experimental, and the design is still
evolving and subject to change. Later versions may break ABI compatibility,
requiring changes or at least a rebuild of any module that depends on it.