ent parser matches the input
            or an exception is emitted. Using on_error(), that exception can be handled
            by calling a handler with the context at which the parsing failed can
            be reported.
          </p>
<p>
            The expect directive parses an operand parser expression which may be
            a single parser or a complex parser expression like a sequence.
          </p>
<p>
            Single parser:
          </p>
<pre class="programlisting"><span class="identifie