mputeroutput"><span class="identifier">a</span> <span class="special">|</span> <span class="identifier">b</span></code>.
              Try <code class="computeroutput"><span class="identifier">a</span></code> first. If it
              succeeds, good. If not, try the next alternative, <code class="computeroutput"><span class="identifier">b</span></code>.
            </li>
<li class="listitem">
              Optionals: e.g. -p. Match the parser p zero or one time.
            </li>
</ol></div>
<p>
          