 \b \t \v \f \n and \r to be recognised,
                    all other Perl-style escape sequences invoke undefined behavior
                    according to the POSIX standard, but are in fact recognised by
                    Boost.Regex).
                  </p>
                </td>
</tr>
</tbody>
</table></div>
<p>
          The following options may also be set when using POSIX extended regular
          expressions:
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<