Here and Now

Here and Now is a Fallout 2, Fallout 3, Fallout: New Vegas, Fallout Tactics, J.E. Sawyer's Fallout Role-Playing Game and Lionheart perk.

This perk "advances the character to the next experience level, if available, with all advantages that entails" - Except one advantage. The level you just gained has no perk, as Here and Now effectively disappears after giving you another level. In simpler terms, you level up again at the cost of a perk.