Provide method of escaping values containing `lookup` identifiers

This is an edge case (and there are ways around it) but consider the following example of a value that starts with a #:

function myAction(opts) {
  return this.lookup(opts)
}

chain
  .myAction({
    id: '!random'
  , color: '#cccccc' 
  })

A couple of options offhand would be:

• Introduce a control character to escape e.g. \#foo, \!bar
• Provide a built-in function that just reflects the value e.g. !literal("#ccc")
  • At minimum this is a viable workaround, since quoted function arguments do not pass through lookup