Args: HASH(0x18241f8) | deep | fish | tuna
  Key = deep
  Adding/using 'deep' of existing hash.
Args: SCALAR(0x224fa4) | fish | tuna
  Key = fish
  Adding 'fish' to new hash: HASH(0x1890b98)
Args: SCALAR(0x1890ba4) | tuna
  Value = 'tuna'

Args: HASH(0x18241f8) | deep | deeper | fish | halibut
  Key = deep
  Adding/using 'deep' of existing hash.
Args: REF(0x224fa4) | deeper | fish | halibut
  Dereferencing REF(0x224fa4) to get HASH(0x1890b98)
  Key = deeper
  Adding/using 'deeper' of existing hash.
Args: SCALAR(0x1890bb0) | fish | halibut
  Key = fish
  Adding 'fish' to new hash: HASH(0x18af2c0)
Args: SCALAR(0x18af2cc) | halibut
  Value = 'halibut'

The resulting leaves are: 'tuna' and 'halibut'

Dump: { deep => { deeper => { fish => "halibut" }, fish => "tuna" } }