Accessing variables from closure

test.js

var vm = require('vm');
var Debug = vm.runInDebugContext('Debug');

Debug.setListener(function (event, exec_state) {
  if (event !== Debug.DebugEvent.Break) return;
  try {
    console.log(exec_state.frame(0).evaluate('inner'))
  } catch (err) {
    console.log(err)
  }
});

function fails() {
  var inner = 'inner';
  var breakpoint = function () {
    debugger;
  }
  breakpoint();
}

function works() {
  var inner = 'inner';
  var breakpoint = function () {
    var ref = inner;
    debugger;
  }
  breakpoint();
}

works();
fails();

$ node test.js
StringMirror { type_: 'string', value_: 'inner', handle_: 8 }
[ReferenceError: inner is not defined]