title: Haskell regex behaves unexpectedly
body: <p>At first I should say that my regex knowlege is <a href="https://regex101.com" rel="nofollow">https://regex101.com</a> - compilant. I don't know if I'm getting wrong the haskell part or the regex part:</p>
  
  <p>I'm trying to use regex to match out domain of a website (stackoverflow.com out of meta.stackoverflow.com). For demo, I'm using simple regex "[\w]+.[\w]+$" which behaves correctly at <a href="https://regex101.com" rel="nofollow">https://regex101.com</a>. However, in haskell:</p>
  
  <pre><code>λ&gt; import qualified Text.Regex.TDFA as RX
  λ&gt; "google.com" RX.=~ "[\\w]+\\.[\\w]+$" :: String
  ""
  λ&gt; "google.com" RX.=~ "[\\w]+\\.[\\w]+$" :: Bool
  False
  </code></pre>
  
  <p>What is causing this behavior and how can I fix it?</p>
  
  <p>GHCI version is 7.10.3,
  regex-tdfa version is 1.2.1</p>