examples-3.x-dev/modules/render_example/render_example.routing.yml

render_example.description:
  path: '/examples/render-example'
  defaults:
    _controller: '\Drupal\render_example\Controller\RenderExampleController::description'
  requirements:
    _permission: 'access content'

render_example.altering:
  path: '/examples/render-example/altering'
  defaults:
    _form: '\Drupal\render_example\Form\RenderExampleDemoForm'
    _title: 'Alter pages and blocks'
  requirements:
    _permission: 'access content'

render_example.arrays:
  path: '/examples/render-example/arrays'
  defaults:
    _controller: '\Drupal\render_example\Controller\RenderExampleController::arrays'
  requirements:
    _permission: 'access content'