I tried this script 

---
use Data::Dumper;

$our_hash = {
    'Cows' => {
        'Brown' => undef,
        'Green' => undef,
        'Strawberry' => {
            'Spotted' => undef,
            'Solid' => undef
        },
        'Orange' => undef
    },
    'Dogs' => {
        'Purple' => {
            'Spotted' => undef,
            'Solid' => undef
        }
    }
};

print Dumper(\$our_hash);
---

and it prints out what you want

---
perl test.pl
$VAR1 = \{
            'Dogs' => {
                        'Purple' => {
                                      'Spotted' => undef,
                                      'Solid' => undef
                                    }
                      },
            'Cows' => {
                        'Green' => undef,
                        'Brown' => undef,
                        'Strawberry' => {
                                          'Spotted' => undef,
                                          'Solid' => undef
                                        },
                        'Orange' => undef
                      }
          };
----

This means you have to install Data::Dumper, but isn't it
allready there, e.g. at <yourPerlDir>/lib/Data/Dumper.pm?