gistfile1.rb

# Ruby's awesome constant-resolution rules.

module X
    A = 5
end

module X
    class Y
        def z
            A
        end
    end
end
puts X::Y.new.z

class X::B
    def z
        A
    end
end

module X
    class B
        def omega
            A
        end
    end
end

puts X::B.new.omega
puts X::B.new.z    # oops, exception raised, can't find X::B::A!