%globally_shared_hash = (
       $source1 => { $target2 => $bv1_2,
                     $target3 => $bv1_3,
                     $target4 => $bv1_4,
                     ...
                 },
       $source2 => { $target1 => $bv2_1,
                     $target3 => $bv2_3,
                     $target4 => $bv2_4,
                     ...
                 },
        ...
   );