What is the difference between these declarations?

my (@a) = ();   # @a contains an empty list
my ($b) = {};   # $b contains a ref to an empty (unnamed) hash
my (@c) = [];   # @c contains a ref to an empty (unnamed) array
my (%d) = ();   # %d contains an empty list
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You may want to (re-)read the documentation on basic data types and references and nested data structures.

— Arien