"using" in coffeescript

using.coffee

window.using = (namespaces..., block) ->
  context = {}
  for ns in namespaces
    for k, v of ns
      if context[k]?
        throw "Unable to import namespace: symbol [#{k}] already imported!"
      context[k] = v
  block(context)

with.coffee

doSomethingToo = =>
  using MyApp.Models, MyApp.Util, MyApp.Widgets, (ctx) =>
    book = new ctx.Book
    author = new ctx.Author
    thing = new ctx.Thinger ctx.escape(book.get('name')), ctx.escape(author.get('name'))

without.coffee

doSomething = =>
  book = new MyApp.Models.Book
  author = new MyApp.Models.Author
  thing = new MyApp.Widgets.Thinger MyApp.Util.escape(book.get('name')), MyApp.Util.escape(author.get('name'))