foo.rb

require 'celluloid'

class C
  include Celluloid

  def initialize(&block)
    @block = block
  end

  def call
    @block.call
  end
end

class D
  include Celluloid

  def run
    c = C.new { puts 'foo' }
    c.call
  end
end

D.new.run

Output

foo
D, [2013-05-11T00:39:46.596057 #48493] DEBUG -- : Terminating 2 actors...
D, [2013-05-11T00:39:46.596526 #48493] DEBUG -- : Shutdown completed cleanly