title: How to append to the clipboard
body: <p>I know how to copy to the clipboard but how can I append to it?</p>
  
  <p>I use this in my code:</p>
  
  <pre><code>let @+ =  my_expression
  </code></pre>
  
  <p>but that overwrites the clipboard.</p>
  
  <p>I know that I can use the registers a-z to append to:</p>
  
  <pre><code>let @B = my_expression
  </code></pre>
  
  <p>which appends to register b, but what do I when I want to append to the clipboard?</p>