n-whitespace character: <tt>[^\s]</tt></td></tr>
 <tr><td valign="top" headers="construct predef"><tt>\w</tt></td>
     <td headers="matches">A word character: <tt>[a-zA-Z_0-9]</tt></td></tr>
 <tr><td valign="top" headers="construct predef"><tt>\W</tt></td>
     <td headers="matches">A non-word character: <tt>[^\w]</tt></td></tr>

 <tr><th>&nbsp;</th></tr>
 <tr align="left"><th colspan="2" id="posix">POSIX character classes</b> (US-ASCII only)<b></th></tr>

 <tr><td valign="top" headers="construct posix"><t