title: How to replace substring in mongodb document
body: <p>I have a lot of mongodb documents in a collection of the form:</p>
  
  <pre><code>{
  ....
  "URL":"www.abc.com/helloWorldt/..."
  .....
  }
  </code></pre>
  
  <p>I want to replace <code>helloWorldt</code> with <code>helloWorld</code> to get:</p>
  
  <pre><code>{
  ....
  "URL":"www.abc.com/helloWorld/..."
  .....
  }
  </code></pre>
  
  <p>How can I achieve this for all documents in my collection?</p>