...
use constant NUM_CHILDREN => 20;
my $num_children = 0;
my $child_index = 0;
my $pm = Parallel::ForkManager->new(NUM_CHILDREN);

$pm->run_on_start( sub {
	my ($pid,$ident)=@_;
	write_file(DIR."/daemon_${ident}.pid", $pid);
	$num_children++;
	msg("$ident) Starting $pid");
});

$pm->run_on_finish( sub {
	my ($pid, $exit_code, $ident, $exit_signal, $core_dump, $job) = @_;
	$num_children--;
	msg("${ident}) Process completed: @_");
	if ($daemon->{'identity'}{'status'} > 0) {
 		startChild($ident);
	}
});
	
# reaper subroutine
sub REAP {
	while (1) {
		my $id = waitpid( -1, WNOHANG);
		if ($id == -1) {
			return;
		}
		if ($id > 0) {
			msg("JUST REAPED $id");
		}
	}
	
	$SIG{CHLD} = \&REAP;
}

$SIG{CHLD} = \&REAP;

# start all the child processes
startChildren();

sub startChildren {
	for (1..NUM_CHILDREN) {
		startChild();
	}

	$pm->wait_all_child;
	
	msg('All children are done.');
}

sub startChild {
	my $child_id = 'child_'.++$child_index;
	my $job = shift(@{$daemon->{jobs}});
 	$job->{process_id} = $child_id;
	$pm->start($child_id) and next;
	process($job);
	$pm->finish(0, $job);
}
...