title: BaseX: Updates are not written back
body: <p>I am trying to run the following query in BaseX, </p>
  
  <pre><code>let $c := doc('t.xq')//entry return (replace value of node $c/author with 'BaseX' )
  </code></pre>
  
  <p>The input file <code>t.xq</code> is</p>
  
  <pre><code>&lt;entry&gt;
      &lt;title&gt;Transform expression example&lt;/title&gt;
      &lt;author&gt;BaseX Team&lt;/author&gt;
    &lt;/entry&gt;
  </code></pre>
  
  <p>I expect it to return the modified data, but it executes and return nothing.
  it says <code>Updates are not written back</code></p>
  
  <p>How can I see the modified <code>entry</code>?  which commands return the altered data?</p>