DB<6> $hr={a=>{b=>{c=>1}}};

  DB<7> $hrf={%$hr}

  DB<8> eval Data::Dumper->Dump ([$hr],['hrd']) # Deepcopy via eval der Serialisierung

  DB<9> print Data::Dumper->Dump ([$hr,$hrf,$hrd],[qw/hr hrf hrd/])
$hr = {
        'a' => {
                 'b' => {
                          'c' => 1
                        }
               }
      };
$hrf = {
         'a' => $hr->{'a'}
       };
$hrd = {
         'a' => {
                  'b' => {
                           'c' => 1
                         }
                }
       };
  DB<10> x $hr,$hrf,$hrd
0  HASH(0x8a4b000)
   'a' => HASH(0x8a5f5c0)
      'b' => HASH(0x87f36a0)
         'c' => 1
1  HASH(0x8a5f770)
   'a' => HASH(0x8a5f5c0)
      -> REUSED_ADDRESS
2  HASH(0x8af90d0)
   'a' => HASH(0x8b154b0)
      'b' => HASH(0x8a55af0)
         'c' => 1