title: Match string that doesn't contain a specific word
body: <p>I'm working with ruby with the <code>match</code> method and I want to match an URL that doesn't contain a certain string with a regular Expression:
  ex:</p>
  
  <pre><code>http://website1.com/url_with_some_words.html
  http://website2.com/url_with_some_other_words.html
  http://website3.com/url_with_the_word_dog.html
  </code></pre>
  
  <p>I want to match the URLs that doesn't contain the word <code>dog</code>, so the 1st and the 2nd ones should be matched</p>