The cypress mulch is moist inside the bag. It won't stay that way. In a couple days, the mulch will dry out and the humidity will drop a lot. I wouldn't keep putting holes in the cage. Just remember, snakes do come across wet areas once in a while in the wild and have to deal with it. If you are very concerned, put newspaper over the mulch in order to keep the snake dry. After a few days though, humidity will drop to the normal amount in your house.
Star