The same file may contain both source code and its LaTeX documentation, and can be executed either by the PLaSM interpreter or by a LaTeX typesetting environment. This behavior is readily obtained by toggling between sources and comments though appropriately using the character %, which is both the comment toggle switch in PLaSM, and the start of a comment line in LaTeX.
For better typesetting results, use the LaTeX package Listings to add source code listings to LaTeX documents. It supports highlighting of all the most common languages, including PLaSM, and it is highly customizable.