Playing with Ruby for QuickPiet interpreter

piet.rb

#! /usr/bin/env ruby

class Recorder
  def push amt
    puts "push: #{amt}"
  end

  def add
    puts "add"
  end

  def macro name, &macro_def
    puts "macro"

    # first way; didn't work
    # self.define_method name &macro_def

    # second way; works
    self.class.send(:define_method, name.to_s, &macro_def)
  end
end

def quickpiet &script
  recorder = Recorder.new

  recorder.instance_eval &script
end

quickpiet do
  macro plus2 do
    push 2
    add
  end

  push 2

  plus2
end

I am looking for clean/simple way to expose quick piet commands w/o other ruby code and with a minimal added globally. Suggestions appreciated.

I was expecting this to output:
macro
push: 2
push: 2
add

instead I got

./piet.rb:27: undefined local variable or method plus2' for #<Recorder:0x1001692d8> (NameError) from ./piet.rb:23:ininstance_eval'
from ./piet.rb:23:in `quickpiet'
from ./piet.rb:26

Figured it out, error above was red herring b/c I didn't use a string or symbol for the macro method invocation.

next problem was accessing define_method correctly (As @adkron pointed out) since it is private to the class and not an instance method