my %country= (
  'United States' => {
      Ohio => {
         'Franklin County' => {
             Columbus => [1, 3.14159, 2.71828],
             Delaware => [2, 3, 5, 7, 11, 13],
          },
         'Crawford County' => {
             Galion => [419, 468, 1708],
          },
         'Summit County' => [1.59, 2.78, 3.62],
      },
      Iowa => [1.9999, 3],
  },
  'Jamaica' => [ 4.512, 1.8, 3],
);

recursivelyprintsum(0, World => \%country);

sub recursivelyprintsum {
  my ($level, $label, $data) = @_;
  if (ref $data eq 'ARRAY') {
    my $value; $value += $_ for @$data;
    print "\t" x $level;
    print "$label:\t$value\n";
    return $value;
  } elsif (ref $data eq 'HASH') {
    print "\t" x $level;
    print "$label:\n";
    my $subtotal;
    foreach my $unit (keys %$data) {
      $subtotal += recursivelyprintsum($level + 1, $unit, $$data{$unit});
    }
    print "\t" x $level;
    print "$label total:\t$subtotal\n";
    return $subtotal;
  } else {
    # $data must actually be $datum.
    print "\t" x $level;
    print "$label:\t$data\n";
    return $data;
  }
}