test.rb

def do_until_false first_input, some_proc
  input  = first_input
  output = first_input
  while output
    input  = output
    output = some_proc.call input
  end
  input
end



build_array_of_squares = Proc.new do |array|
  last_number = array.last
  if last_number <= 0
    false
  else
    #  Take off the last number...
    array.pop
    #  ...and replace it with its square...
    array.push last_number*last_number
    #  ...followed by the next smaller number.
    array.push last_number-1
  end
end
always_false = Proc.new do |just_ignore_me|
  false
end
puts do_until_false([5], build_array_of_squares).inspect
yum = 'lemonade with a hint of orange blossom water'
puts do_until_false(yum, always_false)
[25, 16, 9, 4, 1, 0]
lemonade with a hint of orange blossom water