I like your approach a lot. I would suggest compiling your .prd file into a Perl Module. This makes Parse::RecDescent work faster, since it doesn't have to compile the grammar each time. There is a command line variant for this purpose, from the docs:

> perl -MParse::RecDescent - grammar Yet::Another::Grammar
[download]

Where grammar is your .prd file name and Yet::Another::Grammar is the name of its top level class.

Phil