Some nested data structure

Q

Assume that $ref refers to a scalar, an array, a hash or to some nested data structure. Explain the following statements:

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A

$$ref; # returns the scalar pointed by $ref.
$ref->[0]; # returns the first element of the array pointed by $ref.
@$ref; # returns the contents of the array, (or number of elements of the array in scalar context) pointed by $ref.
$ref->[0][5]; # returns the sixth element in the first row of the array pointed by $ref.
@{$ref->{key}} # returns the contents of the array stored as the value of the key "key" in the associated array pointed by $ref.

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