code class="computeroutput"><span class="identifier">a</span>
            <span class="special">|</span> <span class="identifier">b</span></code>,
            matches one of two or more operands (<code class="computeroutput"><span class="identifier">a</span></code>,
            <code class="computeroutput"><span class="identifier">b</span></code>, ... etc.):
          </p>
<pre class="programlisting"><span class="identifier">a</span> <span class="special">|</span> <span class="identifier">b</span> <span cla