title: How to match {1,0} with a regular expression
body: <p><code>?</code> or <code>{0,1}</code></p>
  <p>will <strong>match</strong> some pattern when necessary, but now I want to do it reversely.</p>
  <p>Say, <strong>don't match</strong> if necessary.</p>
  <p>What is the solution?</p>