my $num  = 5;

sub get_latest {
  my ($year, $mon, $day) = @_;
  my @arr;
  
  if ($year && $mon && $day) {
    my $h = $d_dbd->{$year}->{$mon}->{$day};
    @arr = keys(%$h);
  }
  elsif ($year && $mon) {
    my $h = $d_dbd->{$year}->{$mon};
    for (sort {$a <=> $b} (values %$h)) {
      push(@arr, keys(%$_));
      last if (scalar(@arr) > $num);
    }
  }
  elsif ($year) {
    my $h = $d_dbd->{$year};
    for my $m (sort {$a <=> $b} (values %$h)) {
      for (sort {$a <=> $b} (values %$m)) {
        push(@arr, keys(%$_));
        last if (scalar(@arr) > $num);
      }
    }
  }
  else {
    for my $y (keys %$d_dbd) {
      my $h = $d_dbd->{$y};
      for my $m (sort {$a <=> $b} (values %$h)) {
        for (sort {$a <=> $b} (values %$m)) {
          push(@arr, keys(%$_));
          last if (scalar(@arr) > $num);
        }
      }
    }
  }

  return extract(\@arr);
}

sub extract {
  my ($arr) = @_;
  
  my @p;
  my @arr = @$arr;
  
  if (scalar(@arr) > $num) {
    for (1..$num) {
      my $rand = int(rand(scalar(@arr)));
      push(@p, splice(@arr, $rand, 1));
    }
  }
  else {
    @p = @arr;
  }
  return \@p;
}