deferred_evaluation.rb

# ==========================
# Spell: Deferred Evaluation
# ==========================

# Store a piece of code and its context in a proc or lambda for evaluation later.

class C
  def store(&block)
    @my_code_capsule = block
  end

  def execute
    @my_code_capsule.call
  end

end

obj = C.new
obj.store { $X = 1 }
$X = 0
obj.execute
$X # => 1

# For more information: http://www.pragprog.com/titles/ppmetr/metaprogramming-ruby