Well, personally, I think a false bottom is the way to go, even if you don't want a water feature, but if you don't want to do that, or if this is just a very small terrarium, I'd use gravel. Perlite will retain water, something you don't really want a drainage layer to do, and gravel just looks more natural. Something you could also consider is clay pellets. These are sold under various brand names (Leca, Hydroton, Aliflor), and would actually serve as both good drainage AND the substrate. You would put about 3-4" of these clay balls into the tank (presoaked, something you need to do), fill the tank about 1" with water, and plant your plants. The clay balls wick up moisture from the bottom, remaining evenly moist, at the same time as being an very well-aerated medium for the plants to grow in, and they won't break down over time, and you shouldn't get the smell that happens with potting soil, AND they can be sterilized and are totally safe for animals. All you need to do is keep about an inch of water in the bottom of the tank. Granted, it's not the most natural-looking substrate, but in time the surface would be covered with plants and moss, and you could always cover up the side views (on the outside of the tank) with something. Oh yeah, they're also more lightweight than gravel.

False bottom if you can..if you do want to use the hydroton and hate the looks...then before you fill the tank, coat (to the depth of the substrate) the inside of the tank with black silicone, wait till it dries and trim the edge with a razor blade for a professional, cleaner look.