anchor.diff:  
       /// Run Gaia from the F# repl.
       let runFromRepl runWhile targetDir sdlDeps form world =
  +        RefWorld := world
  +        WorldChangers.Clear ()
           run3 runWhile targetDir sdlDeps form world
   
       /// Run Gaia in isolation.
  
positive.code:         | Right sdlDeps ->
              match attemptMakeWorld plugin sdlDeps with
              | Right world ->
                  let _ = run3 tautology targetDir sdlDeps form world
                  Constants.Engine.SuccessExitCode
              | Left error -> failwith error
  
negative.code:             | _ -> World.choose world
  
      let private run3 runWhile targetDir sdlDeps (form : GaiaForm) world =
          let world = attachToWorld targetDir form world
          populateCreateComboBox form world
          populateTreeViewLayers form world
  