title: Append or prepend selected text to a file in Vim
body: <p>In Vim, is there a way to move the selected text into <code>&lt;current_file&gt;.bak</code>, appending or prepending?
  If possible, the backup file should not be displayed.</p>
  
  <p>I envision the workflow to be:</p>
  
  <ol>
  <li>Select some text</li>
  <li>Type <code>:sbak</code></li>
  <li>The selection is saved into <code>&lt;current_file&gt;.bak</code></li>
  </ol>