title: Ruby: How do I use regex to return all matches?
body: <p>I can intersect two arrays by doing:</p>
  
  <pre><code>keyphrase_matches = words &amp; city.keywords
  </code></pre>
  
  <p>How can I achieve the same thing using regular expression? I want to test one array against a regular expression and get a new array with the matches.</p>