recursive.rb

def match?(obj)
  case obj
  in [1, 2, [3, 4]]
    p :match
  else
    p :not_match
  end
end

obj1 = Object.new
obj1.define_singleton_method(:deconstruct) do
  p :obj1_deconstruct
  obj2 = Object.new
  obj2.define_singleton_method(:deconstruct) do
    p :obj2_deconstruct
    [obj1]
  end
  [1, 2, obj2]
end

match?(obj1)