, this behavior is consistent with the Unix utility
        <code class="computeroutput"><span class="identifier">egrep</span></code>, and with grep when
        used with the -E option.
      </p>
<h5>
<a name="boost_regex.syntax.basic_extended.h30"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_extended.awk"></a></span><a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.awk">awk</a>
      </h5>
<p>
        In addition to the <a class="link" href="basic_extended