rules, subrules may be defined only once. Redefining a subrule is illegal 
  and will result to a compile time assertion.</p>
<h3>Separators [ , ]</h3>
<p>While rules are terminated by the semicollon <tt>';'</tt>. Subrules are not 
  terminated but are separated by the comma: <tt>','</tt>. Like Pascal statements, 
  the last subrule in a group may not have a trailing comma.</p>
<pre><span class=identifier>    </span><span class=identifier>a </span><span class=special>= </span><span class=identifier>ch_p</sp