+calc_age_price($age, $price, 0),       $age <  2;                        # -- (1)
+calc_age_price($age, $price, $result), $age < 12, $result = $price / 2;  # -- (2)
+calc_age_price($age, $price, $price);                                    # -- (3)

,calc_age_price(  0, 100, $result), printn("乳児料金:", $result), next; # 乳児料金を表示
,calc_age_price( 10, 100, $result), printn("子供料金:", $result), next; # 子供料金を表示
,calc_age_price( 20, 100, $result), printn("大人料金:", $result), next; # 大人料金を表示
