depends. What's the wall made of?

Unless it's a tiny section of roof, dumping a downspout's worth of stormwater into a perf pipe behind a wall wouldn't be my choice.

Marcinde's point should be well taken.

My drainage engineering consultant would red line/ red flag that type of connection in a heart beat.

Thanks for responding. They are crestone II retaining wall blocks from Menard's. Concrete another words. You may be right about the downspout but it was either that or have it run behind the wall, on top of the dirt, then drain down the top/front of the wall. The way I ran it, the downspout ties into the end part of the retaining wall drainage pipe with a "T" connector. One direction it goes along the wall and the other it goes to an opening out the wall. This is where I thought most of the water from the downspout would drain.

Absolutely don't arrange the drainage like this. You are supposed to be draining the wall, not supplying the back side of it with an abundance of extra water. On paper, Trav, your scheme may "work out" as something that might "fly" okay, but in real life, it won't.