Example.rb

## Ruby Quiz #666

module CompileSite; end

def compile(name, source)
  CompileSite.class_eval <<-RUBY
    def #{name}(locals)
      Thread.current[:tilt_vars] = [self, locals]
      class << self
        this, locals = Thread.current[:tilt_vars]
        this.instance_eval do
          #{source}
        end
      end
    end
  RUBY
end

def render(name, scope, locals, &blk)
  scope.__send__(name, locals, &blk)
end

module Helper
  A = "A"
end

class Scope
  include CompileSite
  include Helper
  B = "B"
end

class ScopeB < Scope
  B = 'C'
end

compile('hello', <<-RUBY)
  if locals.nil?
    yield
  else
    [locals, A, B, yield, render(:hello, self, nil) { 'Y2' }, yield, locals].join(" ")
  end
RUBY

CompileSite.instance_method(:hello)

res = render(:hello, Scope.new, "L") { "Y1" }
res2 = render(:hello, ScopeB.new, "L") { "Y1" }

if res == "L A B Y1 Y2 Y1 L" and res2 == "L A C Y1 Y2 Y1 L" 
  puts "YOU DID IT!"
else
  puts "Failed:", res, res2
end

Merged. Passes all tests on 1.8.7. I'm pulling down the latest 1.9.1 now. Review appreciated.