Perl救命病棟より無名ハッシュのプライマリーキー

use strict;
use warnings;
use Data::Dumper;

my %aa;
$aa{primary_key}{key1} = 100;
$aa{primary_key}{key2} = 200;

my %bb;
$bb{primary_key} = {
        key1 => 100,
        key2 => 200,
};

print Dumper \%aa;
print Dumper \%bb;
__END__
$VAR1 = {
          'primary_key' => {
                             'key2' => 200,
                             'key1' => 100
                           }
        };
$VAR1 = {
          'primary_key' => {
                             'key2' => 200,
                             'key1' => 100
                           }
        };