$hash{A}{B}{C}{D}{one} = "1";
$hash{A}{B}{C}{D}{two} = "2";
$hash{A}{B}{C}{D}{thr} = "3";

$hash{A}{B}{C}{E}{one} = "4";
$hash{A}{B}{C}{E}{two} = "5";
$hash{A}{B}{C}{E}{thr} = "6";

##</code><code>##

foreach my $key (sort {$a cmp $b} keys "D", "E") {
 print "$hash{$key}";
} 

##</code><code>##

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

my %hash;

$hash{A}{B}{C}{D}{one} = "1";
$hash{A}{B}{C}{D}{two} = "2";
$hash{A}{B}{C}{D}{thr} = "3";

$hash{A}{B}{C}{E}{one} = "4";
$hash{A}{B}{C}{E}{two} = "5";
$hash{A}{B}{C}{E}{thr} = "6";

foreach my $key (keys %{$hash{A}{B}{C}{E}}, %{$hash{A}{B}{C}{D}}) {

    print "$key\n";

}

##</code><code>##

thr
one
two
thr
3
one
1
two
2