character sequence.
          </li>
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            A pattern is a rule expressed as a regular expression and describing
            how a particular token can be formed. For example, <code class="literal">[A-Za-z][A-Za-z_0-9]*</code>
            is a pattern for a rule matching C++ identifiers.
          </li>
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            Characters between tokens are called whitespace; these include spaces,
            tabs, newlines, and formfeeds. Many people also count comments a