for (key in $*) {
  @key_counts[key] += 1;
}
@record_count += 1;

end {
  for (key in @key_counts) {
      @key_fraction[key] = @key_counts[key] / @record_count
  }
  emit @record_count;
  emit @key_counts, "key";
  emit @key_fraction,"key"
}