unless Object.const_defined? :BindingOfCaller
  $:.unshift File.expand_path '../../lib', __FILE__
  require 'binding_of_caller'
  require 'binding_of_caller/version'
end

outer = 10

class Z
  def z
    u = 10
    A.new.a
  end
end

class A
  def a
    y = 10
    B.new.b
  end
end

class B
  def b
    x = 10
    puts binding.of_caller(0).eval('local_variables')
    puts binding.of_caller(1).eval('local_variables')
    puts binding.of_caller(2).eval('local_variables')
    puts binding.of_caller(3).eval('local_variables')
    puts binding.of_caller(400).eval('local_variables')
  end
end

Z.new.z

# output:
# => x
# => y
# => u
# => outer
# Exception