gistfile1.txt

array = [
  1,
  2,
  [3, 4, 5, [6, 7, 8]],
  [9, 10, 11, 12],
  13
]

@capture = []

def process_array(array)
  array.each do |item|
    if item.class == Fixnum
      @capture.push item
    elsif item.class == Array
      process_array(item)
    else
      puts 'Item is not an integer or array!'
    end
  end
end

process_array(array)

puts @capture.inspect