dentifier">qi</span><span class="special">::</span><span class="identifier">attr</span><span class="special">;</span>
</pre>
<p>
          </p>
<p>
            The use of <code class="computeroutput"><span class="identifier">hold</span><span class="special">[]</span></code>
            here will make sure the changes to the attribute caused by the (failing)
            first alternative will not be visible after the whole parsing succeeded.
          </p>
<p>
</p>
<pre class="programlisting"><span class="id