title: How do I make part of a regular expression optional in Ruby?
body: <p>To match the following:</p>
  
  <pre><code>On Mar 3, 2011 11:05 AM, "mr person" 
  wrote: 
  </code></pre>
  
  <p>I have the following regular expression: </p>
  
  <pre><code>/(On.* (?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) \d{1,2}, [12]\d{3}.* at \d{1,2}:\d{1,2} (?:AM|PM),.*wrote:)/m
  </code></pre>
  
  <p>Is there a way to make the at optional? so if it's there great, if not, it still matches?</p>