title: How to use include? method in ruby
body: <pre><code>vowels = "aeiou"
  "hello".include?(vowels) # ==&gt; false
  </code></pre>
  
  <p>but if I add <code>!</code> to the statement it works fine:</p>
  
  <pre><code>!("hello".include?(vowels) # ==&gt; true
  </code></pre>