title: Search and replace operation
body: <p>I have a list which has URL values like:</p>
  
  <pre><code>http://farm6.static.flickr.com/5149/5684108566_aed8b9b52d_s.jpg
  </code></pre>
  
  <p>How can I change the <code>_s</code> in the end to <code>_m</code> for all occurrences?</p>