title: AWS WAF Regexp issue with lookahead
body: <p>I am building a regexp for AWS WAF using a negative lookahead.</p>
  
  <pre><code>joe(?!(ann|jen))
  </code></pre>
  
  <p>However, I've got back the following error from WAF console</p>
  
  <pre><code>WAFInvalidParameterException: Error reason: The parameter contains formatting that is not valid., field: REGEX_PATTERN_SET, parameter: joe(?!(ann|jen))
  </code></pre>
  
  <p>It seems like the AWS WAF does not support this kind of regexp. I've found this blog
  <a href="https://aws.amazon.com/about-aws/whats-new/2017/10/aws-waf-now-supports-regular-expressions-regex/" rel="nofollow noreferrer">https://aws.amazon.com/about-aws/whats-new/2017/10/aws-waf-now-supports-regular-expressions-regex/</a></p>
  
  <p>Is there anyone having similar issue? can you share how to fix it?</p>