DB<90> $hr2={%$hr1}  # shallow copy
 
  DB<91>  print Data::Dumper->Dump([$hr1,$hr2],[qw/hr1 hr2/])
$hr1 = {
         'a' => {
                  'b' => {
                           'c' => 1
                         }
                }
       };
$hr2 = {
         'a' => $hr1->{'a'}
       };
 
  DB<92> x $hr1,$hr2
0  HASH(0x8b64b78)
   'a' => HASH(0x8b64c18)
      'b' => HASH(0x8af9120)
         'c' => 1
1  HASH(0x8b156c0)
   'a' => HASH(0x8b64c18)
      -> REUSED_ADDRESS