use Parallel::ForkManager qw( );
 
my @testLists = ...;
my $status = 0;

my $pm = Parallel::ForkManager->new( 2 );

$pm->run_on_finish(sub {
   my ( $pid, $exit_code, $ident ) = @_;
   $status += $exit_code;
});
 
for my $list ( @testLists ) {
   $pm->start and next;

   my $status = regressions( $opts, $list );
   $status = 255 if $status > 255;
   
   $pm->finish( $status );
}

$pm->wait_all_children();