Cannot retrieve empty keys from request using Apache2::Request.param

Hi all,

i'm using mod_perl in order to retrieve all keys from a POST request with:

my $request = Apache2::Request->new($r);
my $data = $request->param();

When i receive something like
key1=value1&key2=&key3=value3
$data contains all 3 keys

but with
key1=value1&key2&key3=value3
$data contains only 2 keys: key1 and key2&key3

Is there a way to retrieve all the 3 keys like the first case? Any suggestions?
Thank you,

Tommaso