Surely stone tools have demonstrated perpendicular attributes. It’s not too far of a stretch to imagine a Palaeolithic hunter aligning an axe head against a handle in a way that made it even on either side.
I haven't seen any stone tools with perpendicular sides. In fact, I don't know of any other 90-degree stonework until the T-stones at Gobekle Tepe. If you could point me to some examples I'd be very much interested in knowing about them.