my $watch = $zkh->watch('timeout' => 10000);
  $zkh->exists('/myzknode', 'watch' => $watch);

  if ($watch->wait()) {
    print "watch triggered on node /myzknode:\n";
    print "  event: $watch->{event}\n";
    print "  state: $watch->{state}\n";
  }
  else {
    print "watch timed out after 10 seconds\n";
  }