Differences in consuming items in Nethack vs Slashem
I have started playing Slash'em extended, and do not know how to quaff potions or eat corpses from the floor without picking them up first. Normally, on alt.nethack.org, I would just hit q and it would pop up a "Quaff from fountain?" command, but that is not the case on Slash'em extended.
SLASH'EM changes the "use item on ground" command to be the item "." in the regular prompt instead of being a separate prompt. You should see "." included in the items you can eat/drink if you're standing on the appropriate square. Select that to eat the item/drink from the fountain.