Perl: Threading with shared multi-dimensional hash

Я пытаюсь поделиться многомерным хешем по нескольким потокам . This hash holds 2 connected key-pairs, I need to know if they are already connected, if they are not, I need to connect them, if not, there is no need to go to the database.

use threads;
use threads::shared;

my %FLUobject2param : shared    = ();

#Start a new thread for every available processor
for (my $i=0;$i<$PROCESSORS;$i++) {
    threads->new(\&handlethread);
}
#Catch if these threads end
foreach my $onthr (threads->list()) {
    $onthr->join();
}

sub handlethread{
    ...
    if(not defined $FLUobject2param{$objectID}{$paramID}){
        $dbh->getObject2Param($objectID,$paramID);
        $FLUobject2param{$objectID}{$paramID} = 1;
    }
}

I keep getting the error Invalid value for shared scalar on the line
if(not defined $FLUobject2param{$objectID}{$paramID}){

This apparently has to do with perl's threads::shared only allowing you to share a single level of shared structure.

How would I still be able to check if this combination is already used over multiple threads ?