---

$$0: &SMALL  { r: 1 }
$$1: &BIG    { r: 100 }
$$2: &LEFT   { x: -1, y: -2 }
$$3: &RIGHT  { x:  1, y:  2 }

map1: # Explicit keys
  r: 10
  x: 1
  y: 2

map2: # Merge one map
  r: 10
  <<: *RIGHT

map3: # Merge multiple maps
  <<: *BIG
  <<: *RIGHT

map4: # Override
  <<: [ *BIG, *LEFT, *SMALL ]
  <<: *RIGHT
  x: 0