my $foo = { };
$foo->{a}->{b}->{c}->{d} = 1;
use Data::Dumper;
print Data::Dumper->Dump([$foo],['foo']);

##</code><code>##

$foo = {
         'a' => {
                  'b' => {
                           'c' => {
                                    'd' => 1
                                  }
                         }
                }
       };

##</code><code>##

print %{$foo->{a}->{d}}


##</code><code>##

my $bar = $foo->{a}->{d};
print %$bar if $bar;