title: Weird syntax error with parens
body: <p>Other than hashes as last argument, you can drop parenthesis in Ruby on method invocations and get consistent results (you still have to mind the priority).</p>
  
  <p>However, I encountered an example where this is not the case:</p>
  
  <pre><code>''.split(/ ./) # =&gt; []
  ''.split /./   # =&gt; []
  ''.split / ./  # !&gt; SyntaxError: unexpected '.'
  </code></pre>
  
  <p>Is this a bug/regression (I tested it with 2.1.2 -> 2.4.1 Rubys)?</p>
  
  <p>Are there other generic cases where dropping the parens doesn't work as expected?</p>
  
  <hr>
  
  <p><a href="https://bugs.ruby-lang.org/issues/13371" rel="nofollow noreferrer">Reported it</a>, lets see.</p>
  
  <hr>
  
  <p><strong>Update</strong>: The ticket was rejected a bit ambiguously. It's not clear if it's a bug or not, but it won't get fixed and using <code>%r{}</code> in these situations was suggested. The cause is indeed that the opening slash is interpreted as division.</p>