Coco is very light, and does not compact in the same way soil does, so you genuinely dont need the perlite. If you want it, that's fine, but your essentially taking moisture retention out of your media, in lieu of aeration that the medium already has.
As for your response of "I'm not growing in hydro, I'm growing in coco"... they're essentially the same thing. Coco is an inert media, meaning not only is it lifeless, but it lacks any of it's own natural nutrients to help feed the plant, and also lacks buffering ability for pH.
If you intend to grow in coco, or even a coco/perlite mix, you should do some more research specifically on growing in coco, because you'll be mighty disappointed in how your grow progresses, if you go into a coco grow, and treat it the way you treat soil.
Not to say you lack experience, but for people who have less experience growing, soil is the best way to get started. Coco is more of a challenge, but I've seen monsters grown in coco, so it can be a great medium, provided you know what your doing.
No matter what you decide, good luck! Just be sure you take your time to plan properly, and learn everything you can before you get started, and you'll do fine