If you are to filter by either first number, second or id I'd suggest to use

$hoh->{$id} = { first_number  => $first_num,
                second_number => $second_num};
[download]

and then to filter simply use grep

# Retrieve all IDS were first number is 2
my @ids = grep { $hoh->{$_}->{first_number} == 2 } keys $hoh;
[download]