title: replace escape character in flex
body: <p>I use flex to work on a scanner to replace <code>\"</code> with <code>"</code>; and <code>\\</code> with <code>\</code>.</p>
  
  <p>so my code is like</p>
  
  <pre><code>%%
  \\"    \";
  \\\    \\;
  </code></pre>
  
  <p>but when I compile, I get an error message like <code>missing quote</code>.
  I think it's the right regular expression, did I get wrong or it's something special with flex?</p>