is expected that the input must match
            a particular parser or the input is invalid. Such cases generally arise
            after matching a portion of a grammar, such that the context is fully
            known. In such a situation, failure to match should result in an exception.
            For example, when parsing an e-mail address, a name, an "@"
            and a domain name must be matched or the address is invalid.
          </p>
<p>
            The expect directive requires that the argum