#!/usr/bin/perl -w
use strict;
use warnings;
use Test::More qw(no_plan);

my $expected = 'set2 set3 set4 set1 ';

my $HoHoA = {
              'set1' => {
                         'AAAAAAA' => [ ['1','BOOK'],['2','PENCIL'] ],
                         'BBBBBBB' => [ ['0','CHALK'],['4','PEN'] ],
                       }, 
             # length of 2nd keys = 7 (all the same in 'set1')

              'set2' => {
                         'AAA' => [ ['1','BOOK'],['2','PENCIL'] ],
                         'BBB' => [ ['0','CHALK'],['4','PEN'] ],
                       }, 
             # length of 2nd keys = 7 (all the same in 'set2')

              'set3' => {
                         'AAA' => [ ['1','BOOK'],['2','PENCIL'] ],
                         'BBB' => [ ['0','CHALK'],['4','PEN'] ],
                       }, 
              # length of 2nd keys = 3 (all the same in 'set3')

              'set4' => {
                         'AAAA' => [ ['1','BOOK'],['2','PENCIL'] ],
                         'BBBB' => [ ['0','CHALK'],['4','PEN'] ],
                       }, 
              # length of 2nd keys = 4 (all the same in 'set4')
};

my $got = ''; 
foreach  my $set ( sort { inner_key_length($a) <=> inner_key_length($b) } ( keys %{$HoHoA} ) )
{	
	$got = $got . "$set ";
}

sub inner_key_length {
	my $key = shift or die "no key";
	
	my @keys = keys %{ $HoHoA->{$key} };
	my $length_firstkey = length($keys[0]);

	for my $check_key ( @keys ) {
		 die "inconsistent key length" unless $length_firstkey = length($check_key);
	}
	print "length $key is $length_firstkey\n";
	return $length_firstkey;
}

is($got, $expected);