ches"><i>X</i>, once or not at all</td></tr>
 <tr><td valign="top" headers="construct poss"><i>X</i><tt>*+</tt></td>

     <td headers="matches"><i>X</i>, zero or more times</td></tr>
 <tr><td valign="top" headers="construct poss"><i>X</i><tt>++</tt></td>
     <td headers="matches"><i>X</i>, one or more times</td></tr>
 <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>}+</tt></td>

     <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
 <tr><td valign="top" headers=