#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump;

my @items = (2,14,7,17,1,12,3,4,11,5,13,6,8,10,9,16,15,18);

@items = map { sprintf '%02u', $_ } @items;
dd @items;

@items = sort @items;
dd @items;

my ($odd,$even)=(0,0);
$_ % 2 ? $odd++ : $even++ for @items;
print "Odd = $odd, Even = $even\n";

my %odd_even;
$odd_even{"$odd $even"}++;
dd \%odd_even;               # { "9 9" => 1 }
dd $odd_even{0};             # undef

my $sum;
$sum += $_ for @items;
my $avg = $sum / @items;
$avg = ($avg - int($avg)) >= 0.5 ? int($avg) + 1 : int($avg);

my %average;
$average{$avg}++;
dd \%average;                # { 10 => 1 }
dd $average{0};              # undef