Syntax:

ch:at(string)

Format:
at [location] [command] : execute command at location

Accepts format arguments.

Examples:

mob:at(ch.name.." dance")

mob:at("%d say hi there stranger", doggy.room.vnum)

If you want to use functions within your at statement, you'll need to treat the at statement like an old mprog:

mob:at("%d mob mload 9313", wing_vnums[r])