Marpa::HTML::XS is a Perl module that uses Marpa::HTML and Marpa::XS. The documentation is with those two modules.
Marpa::HTML by itself own chooses between Marpa::XS and Marpa::PP. Marpa::HTML runs Marpa::XS if possible, Marpa::PP otherwise. This is what users find most convenient, but there is a downside: since Marpa::XS requires a number of non-Perl dependencies, the cpantesters almost always run with Marpa::PP. This makes it difficult for users to determine if an XS-powered Marpa::HTML has been tested on their system. The lop-sided testing of Marpa::HTML is also a major quality assurance for both Marpa::HTML and Marpa::XS. This module redresses the balance.