How can I check if a Ruby array includes one of several values?

Set intersect them:

a1 & a2

Here’s an example:

> a1 = [ 'foo', 'bar' ]
> a2 = [ 'bar', 'baz' ]
> a1 & a2
=> ["bar"]
> !(a1 & a2).empty? # Returns true if there are any elements in common
=> true