my %hash = (a=>1, b=>2);
my $hashRef = { c=>3, d=>4 };

# For a hash, you can reference the item as you expect:
my $v = $hash{a};

# For a hash ref, you need to either use a double $, or
# use an arrow:
$v = $hashRef->{c};
$v = $$hashRef{c};

##</code><code>##

# Get a reference to %hash
$hashRef = \%hash;

$v = $hashRef->{a};  # $v now holds 1