New Twiddle

components.case-of.js

import Ember from 'ember';

export default Ember.Component.extend({
});

components.case-of.when.js

import Ember from 'ember';

export default Ember.Component.extend({
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

{{#case-of list as |when|}}
  {{#when 'Nil'}}
  
  {{/when}}
	{{#when 'Cons' as |head tail|}}
  
  {{/when}}
{{/case-of}}

{{#with (case-of list 'Cons') as |head tail|}}

{{else with (case-of list 'Nil')}}

{{/with}}

templates.components.case-of.hbs

{{yield}}

templates.components.case-of.when.hbs

{{yield}}

templates.components.when.hbs

When!

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}