title: Replace tags surrounding string only if string contains match
body: <p>I have a file with many lines containing strings surrounded by tags.</p>
  <pre><code>  &lt;tag:identifier&gt;99454&lt;/tag:identifier&gt;
    &lt;tag:identifier&gt;97817(web)&lt;/tag:identifier&gt;
    &lt;tag:identifier&gt;http://www.google.com&lt;/tag:identifier&gt;
    &lt;tag:title&gt;Title String/&lt;/tag:title&gt;
    &lt;tag:creator&gt;Example&lt;/tag:creator&gt;
    &lt;tag:creator&gt;Field&lt;/tag:creator&gt;
    &lt;tag:creator&gt;Country&lt;/tag:creator&gt;
  </code></pre>
  <p>I am trying to find a way to change the tags around each URL. They all start with <code>&lt;tag:identifier&gt;http</code>, so finding which lines contain URLs isn't an issue, I just don't know how I can replace the ending tag too. For example, to <code>&lt;tag:url&gt;http://www.google.com&lt;/tag:url&gt;</code></p>
  <p>What tool can I use to do this?</p>