Perception lets you open the doors in the Superior Temple of Baa (expert needed, one optional door requires master lvl 8).
It also gives you a chance to dodge chest traps when they go off, which could be a bit useful on a healer.
It also lets you loot trash heaps for items. You get diseased instead if your perception isn't high enough.
If also lets you loot skull piles for scrolls. The skull piles come in different varieties depending on which condition they cause: disease, death, etc. The worse the condition, the better the scroll you will get: skull piles of death can drop scrolls of starburst for example. You get the condition instead if your perception isn't high enough.
And it lets you loot gems from crystals like the ones in Snergle's Caverns and Gharik's Forge.
It doesn't let you:
- get rings from campfires (seems random)
- loot gold/gem veins (seems random)
- highlight things in red (mm7/8).