title: Drop log line containing hash character
body: <p>In my Logstash shipper I want to filter out lines commented with the hash character:</p>
  
  <pre><code>#This log row should be dropped.
  But one this should not.
  </code></pre>
  
  <p>I was able to use <code>grep</code> filter, but as it is discouraged (going to be decommissioned), I'm trying to get a <code>grok</code> filter to do it instead. This filter is not working:</p>
  
  <pre><code>grok {
    match =&gt; ["message", "^#.*"]
    drop_if_match =&gt; true
  }
  </code></pre>
  
  <p>I also tried placing the regex in a custom pattern file, but didn't help. Any ideas?</p>