plpgsql direct from C?

Is there an API method to be able to execute pl/pgsql (or any other
language) code directly from C?

Eg (please excuse the line wrapping, and the fact that this doesn't
represent a case where this would actually be useful!)

result = PQexecPL("plpgsql", "IF $1 = 'xyzzy" THEN SELECT * FROM fnord
END IF;", "xyzzy");

?

Thanks

James