before.js

const DREAMLAND = true;

function halp() {
   if (DREAMLAND) {
       let santa = "I do exist"
   }
   console.log(typeof santa) // => undefined
}

compile.js

$traceurRuntime.ModuleStore.getAnonymousModule(function() {
  "use strict";
  var DREAMLAND = true;
  function halp() {
    if (DREAMLAND) {
      try {
        throw undefined;
      } catch (santa) {
        santa = "I do exist";
      }
    }
    console.log((typeof santa === 'undefined' ? 'undefined' : $traceurRuntime.typeof(santa)));
  }
  return {};
});