my $reference_to_value;
if ($reference_to_value = exists $hash{$key}) {
    print "value is $$reference_to_value\n";
}

##</code><code>##

if (exists $hash{$key}) {
    print "value is $hash{$key}\n";
}

##</code><code>##

$hash{$key}{'a'} = 'A';
$hash{$key}{'b'} = 'B';
$hash{$key}{'c'} = 'C';