title: Reclaiming expired keys in Redis
body: <p>I'm trying to solve the following problem in Redis.</p>
  
  <p>I have a list that contains various available keys:</p>
  
  <pre><code>List MASTER:
  111A
  222B
  333C
  444D
  555E
  </code></pre>
  
  <p>I'd like to be able to pop an element off of the list and use it as a key with an expires.  </p>
  
  <p>After the expires is up, I'd like to be able to push this number back onto MASTER for future use.  I don't see any obvious way to do this, so I'm soliciting for a creative one.</p>