title: How can I match Korean characters in a Ruby regular expression?
body: <p>I have some basic validations for usernames using regular expressions, something like <code>[\w-_]+</code>, and I want to add support for Korean alphabet, while still keeping the validation the same.</p>
  
  <p>I don't want to allow special characters, such as <code>{}[]!@#$%^&amp;*()</code> etc., I just want to replace the <code>\w</code> with something that matches a given alphabet in addition to <code>[a-zA-Z0-9]</code>.</p>
  
  <p>Which means username like <code>안녕</code> should be valid, but not <code>안녕[]</code>.</p>
  
  <p>I need to do this in Ruby 1.9.</p>