Exclude logs from fluentd using exclude directive not working

Question

Trying to exclude logs using the grep's exclude directive.

<filter kubernetes.var.log.containers.**>
  @type grep
  <exclude>
    key kubernetes.pod_name
    pattern /^podname-*/
  </exclude>
</filter>

I tried with different key names e.g. container and namespace as well. I am trying to exclude logs from a certain pod using the pattern but it's not working. Using type forward source type to send logs.

Want to exclude logs from certain pods starting with the same name from var log containers.