gistfile1.txt

clm-bshirai:~ bshirai$ rbx
irb(main):001:0> class A
irb(main):002:1> dynamic_method :get_undefined do |g|
irb(main):003:2* g.push_undef
irb(main):004:2> g.ret
irb(main):005:2> end
irb(main):006:1> end
=> #<Rubinius::CompiledCode get_undefined file=(dynamic)>
irb(main):007:0> A.new.get_undefined
=> undefined
irb(main):008:0>