gistfile1.rb

class Object
  def chain_method(with_symbol, &new_method)
    old_method = method with_symbol
    eigenclass = class << self; self; end
    eigenclass.class_eval do
      define_method with_symbol do |*args| new_method[old_method, *args] end
    end
  end
end

def foo(arg)
  print 'in foo: ', arg, "\n"
end

puts
foo 'first call'

chain_method :foo do |old_method, arg |
  puts 'in first block_eval'
  old_method.call arg
end

puts
foo 'second call'

chain_method :foo do |old_method, arg|
  puts 'in second block_eval'
  old_method.call arg
end

puts
foo 'third call'