title: LookAhead not working in JFlex
body: <p>I am trying to use JFlex to build a parser but encounter a very basic issue.
  I want to have this token </p>
  
  <pre><code>[A-Za-z]+_N$ { System.out.println("Noun"); }
  </code></pre>
  
  <p>and have it recognize "car_N" as a "Noun" and NOT recognize "car_NN".
  but it does not work, if I use </p>
  
  <pre><code>[A-Za-z]+_N { System.out.println("Noun"); } 
  </code></pre>
  
  <p>"car_N" get recognize but "car_NN" returns "car_N" as well, this is not what I want.</p>
  
  <p>I wonder anyone here knows how to help?</p>
  
  <p>JFlex and Flex lookahead symbol '$' does not seem to be working</p>