# connect parent
$dbh->connect(...);

#statement 1
$sth=$dbh->prepare($sql);
$sth->execute;
while(($var)=$sth->fetchrow_array) {

	# fork
	$pm->start and next;

	# connect child
	$dbh2->connect(...);

	#statement 2
	$sth2->prepare($sql2);
	$sth2->execute;
	while(($var2)=$sth2->fetchrow_array) {

		# condition
		if($var) {
			# statement 3 that might not be called
			$sth3->prepare($sql3);
			$sth3->execute;
			while(($var3)=$sth3->fetchrow_array) { ... }
			$sth3->finish;
		} else {
			# statement 4 that might not be called
			$sth4->prepare($sql4);
			$sth4->execute;
			while(($var4)=$sth4->fetchrow_array) { ... }
			$sth4->finish;
		}

	}
	# finish statement 2
	$sth2->finish;

	# disconnect child
	$dbh2->disconnect;

	# end fork
	$pm->finish;
	
}
# finish statement 1
$sth->finish;

# disconnect parent
$dbh->disconnect;