Line 22 is not necessary if you use the more common syntax:

my %testHash;
my $hashRef = \%testHash;
$hashRef->{a} = "Hello World!";
my $destref = \$hashRef->{b};
# assign a value to the hash element 'a'
$$destref->[0] = 'How';
$$destref->[1] = 'are';
$$destref->[2]{'c'} = "you";
$$destref->[2]{'d'} = "today?";
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