in CoffeeScript, how can I use a variable as a key in a hash?

For anyone that finds this question in the future, as of CoffeeScript 1.9.1 interpolated object literal keys are supported!

The syntax looks like this:

myObject =
  a: 1
  "#{ 1 + 2 }": 3

See https://github.com/jashkenas/coffeescript/commit/76c076db555c9ac7c325c3b285cd74644a9bf0d2