{
  # initialize counters 
  my %counter = map { $_ => 0 } qw( Ok Warning Error Fatal );

  sub increase_counter {
    my $id = shift;

    die "(E) Specified counter '$id' does not exist!\n"
      if not exists $counter{$id};

    $counter{$id}++;
  }

  sub show_counter {
    for my $k ( sort keys %counter ) {
      printf "%10s : %s\n", $k, $counter{$k};
    }
  }
}

# increase specified counter
increase_counter('Ok');

# show values of all counters
show_counter();