title: Regular expression syntax for "match nothing"?
body: <p>I have a python template engine that heavily uses regexp. It uses concatenation like:</p>
  
  <pre><code>re.compile( regexp1 + "|" + regexp2 + "*|" + regexp3 + "+" )
  </code></pre>
  
  <p>I can modify the individual substrings (regexp1, regexp2 etc).</p>
  
  <p>Is there any small and light expression that matches nothing, which I can use inside a template where I don't want any matches? Unfortunately, sometimes '+' or '*' is appended to the regexp atom so I can't use an empty string - that will raise a "nothing to repeat" error.</p>