$hashref = \%hash; # $hashref is a scalar pointing to %hash
%$hashref   or   %{$hashref}# the same as %hash

$hash{'key'}
# is the same as
$hashref->{'key'}

$hashref->{'key'} = \@array; # Make this key a reference to the array @array
@{$hashref->{'key'}} # the same as @array, the extra brackets {} show you are looking for the array in $hashref->{'key'} and not an array in $hashref

$hashref->{'key'}->[0] # same as $array[0]