title: Evaluate bash/zsh expressions inline
body: <p>I am aware that it's possible to do stuff like</p>
  
  <pre><code>echo `ls` "foobar"
  echo $(ls) "foobar"
  </code></pre>
  
  <p>but when I try to do something like</p>
  
  <pre><code>diff `pip freeze` requirements.txt
  diff $(pip freeze) requirements.txt
  </code></pre>
  
  <p>it fails.</p>
  
  <p>What am I missing here? Thanks!</p>
  
  <p>P.S I am using <code>zsh</code> shell.</p>