use Parallel::ForkManager; # Yadda yadda
local %hash;
$pm = new Parallel::ForkManager(2); # Want use 2 CPUs now (###)

foreach $thingy (@so_30_member_list) {
  my $pid = $pm->start and next;  # (###)
  $hash{$thingy} = &big_heavy_computation_of($thingy);
  $pm->finish; # Terminates the child process (###)
}

&look_at_hash;