title: Why is rubocop asking me to put // around regex when i'm using %r already?
body: <p>I have the following regex </p>
  
  <pre><code>  regexp = %r{
       ((returned|undelivered)\smail|mail\sdelivery(\sfailed)?)
    }x
  </code></pre>
  
  <p>But when I run rubocop on it, it complains that I need to "Use // around regular expression."</p>
  
  <p>How can I get around it?</p>