▽
└─▣ Attr value: foo
  ╟─◈ = "a"s
  ║ ┖─◁ #0 [0,1,0] value 1
  ╟─◈ = "b"s
  ║ ┖─◁ #1 [0,1,0] value 2
  ╙─◈ ^= "c"s
    ┖─◁ #2 [0,1,0] value 3