#!/usr/bin/perl -w
use strict;

my %hash1 = ( A => 1, B => 2, C => 3, D => 4, ); 
my %hash2 = ( D=>1, E =>2, F => 3, G => 4, H => 5, I => 6, J=>7 ); 
my %hash3 = ( J=>1, K =>2, L => 3, M => 4, N => 5, O => 6, P=>7, 
              Q =>8, R =>9, S =>10, T => 11, U =>12, D=>13, );

foreach my $key ( keys(%hash1), keys(%hash2), keys(%hash3) )
{
   print "$key";
}
print "\n";
#prints:ADCBHFJDIGESOJTNPKQMDRLU