title: How can I have logstash drop all events that do not match a group of regular expressions?
body: <p>I'm trying to match event messages with several regular expressions. I was going for the use of grep filter, but its deprecated so I'm trying for the drop with negation. </p>
  
  <p>The functionality I'm looking for is to have all events dropped unless the message matches several regular expressions.  </p>
  
  <p>The filter bellow does not work, but tested individually both expressions work fine. 
  What am I missing?</p>
  
  <pre><code>filter {    
      if ([message] !~ ' \[critical\]:  ' or [message] !~ '\[crit\]: ') {
          drop { }
      }
  }
  </code></pre>