title: Ruby regular express. detect wrong email address such as "hi@myio..io"
body: <p>To detect wrong email address such as "hi@myio..io"</p>
  
  <pre><code>  VALID_EMAIL_REGEX =      /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
    VALID_EMAIL_REGEX_FULL = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z]+)*\.[a-z]+\z/i
  </code></pre>
  
  <p>First one fails. Second suceeds. 
  I don't understand how does this part make it different? <code>(\.[a-z]+)*\.[a-z]</code></p>
  
  <p>Thank you!</p>