de>      </td>
    <td> Matches <code>patt1</code> if <code>patt2</code> does not also match.</td>
    </tr>
    <tr>
    <td><code>-patt</code>              </td>
    <td> Equivalent to <code>("" - patt)</code>.</td>
    </tr>
    <tr>
    <td><code>#patt</code>              </td>
    <td> Matches <code>patt</code> but consumes no input.</td>
    </tr>
    </tbody>
    </table>


    <p>The first part of this document deals with rapidly constructing a simple
    lexer. The next part deals with more advance