class Object
    def x
        "Object's x"
    end
end

class MyClass
    x = "hello"
end

def foo
    Object.new.instance_eval {puts x}
end

def bar
    x = "Hello!"
    Object.new.instance_eval {puts x}
end

foo            #=> Object's x
bar            #=> Hello!
puts MyClass.x #=> Object's x