How to include multiple conditions in one equivalence statement?

I'm trying to trigger a condition if a variable meets one of two values. I'm aware I can express this as:

if x == 5 || x == 6
    execute code...
end

But I was wondering if there was something a bit more elegant in case x has a long name. Something like:

if x == {5, 6}
    execute code...
end

Anyone have any ideas?