title: What is the $() construct?
body: <p>I have been trying to find in the Haskell reference the use of this:</p>
  
  <pre><code>getHomeR = defaultLayout $ do
      setTitle "My Awesome Site"
      $(widgetFile "home")
  </code></pre>
  
  <p>Specifically:</p>
  
  <pre><code>$(widgetFile "home")
  </code></pre>
  
  <p>I know that the $ operator gives precedence to whatever is to the right of it, but I have not been able to comprehend the usage of $(). Anyone?</p>