deep flatten without Array#flatten

#!/usr/bin/env ruby

class Array
  def my_flatten
    return self if empty?
    return self unless any? { |el| el.is_a? Array }
    last_elem = pop
    if last_elem.is_a? Array
      my_flatten + last_elem.my_flatten
    else
      my_flatten << last_elem
    end
  end
end

# specs

class MyArray < Array
  def yeah!
    self << 'Because I can!'
  end
end

my_a = MyArray.new([1, 2, [3, 4, [[5, 6], 7, [8], 9], 10], 11])

samples = [
  [],
  [1],
  [1, 2, 3],
  [1, 2, [3]],
  [[[[[1]]]]],
  [1, 2, [3, 4, [[5, 6], 7, [8], 9], 10], 11],
  my_a
]

samples.each do |sample|
  puts "original array: #{sample}"
  puts "flatten array: #{sample.dup.my_flatten}"
  if sample.dup.my_flatten == sample.dup.flatten
    puts 'green'
  else
    puts 'red'
  end
end