title: Regular Expression Lookbehind and Lookahead numerical test
body: <p>I am attempting to configure a regular expression that matches anything numerical value but 1211 so it will still match variations such as 1212 121 1122, 3411, etc</p>
  
  <p>I am unable to test the below at <a href="http://regexpal.com/" rel="nofollow">http://regexpal.com/</a> as it does not seem to support ?
  
  <pre><code>(1(?!2)|1(?!2)|(?&lt;!1)2|(?&lt;!2)1|[^1211])+|[0-9]{1,4})
  </code></pre>
  
  <p>Am I doing it right and also where can I test it?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>Please note that I need to implement in a rewrite module/filter.</p>