When you say perpendicular, are you wanting to measure if the wall is truly perpendicular to the floor regardless of the angle of the floor or are you concerned with being plumb to vertical?
I am not aware of anything that can do either automatically that is even somewhat affordable. There are some laser based surveying tools available that can measure a wall for vertical but they start at 5 figures and go up from there. If you just need to get some what close, an 8' bubble level might be the most cost effective choice. If you need to be more precise I have had good luck setting a laser plumb bob a know distance from the base of the wall and measuring out at intervals up the wall.
Hope this helps
There are multi type lasers. Like this
But I don’t think it will tell you if it’s a direct 90 as that would take some processing in the laser tool.
A good speed square would do the trick why do you need it to be a laser?
@Nick Solyom I had a Hilti and used it exactly as @mikebags is describing.https://www.boschtools.com/us/en/boschtools-ocs/line-lasers-gcl-25-123123-p/
It’s not automatic, but you could place something like the laser above on your CS mark and then line the side lasers up with your proscenium. Then the cross laser would draw a line US to DS perpendicular to your opening.