$$: ignored
$$tail: ignored

$$ans: &ans 42
$$eu:  &eu  2.72
$$pi:  &pi  3.14

opt:
  bool: true
  int: *ans
  real: *pi
  imag: 2.72i
  cmplx: -3.14+2.72i
  str: petsc

$$1: &seq-bool [true, false]
$$2: &seq-int  [123, 456, 789]
$$3: &seq-real [*pi, *eu]
$$4: &seq-str  [abc, ijk, fgh]

seq1: {
  bool: *seq-bool,
  int:  *seq-int,
  real: *seq-real,
  str:  *seq-str,
}

seq2:
  bool:
    - true
    - false
  int:
    - 123
    - 456
    - 789
  real:
    - *pi
    - *eu
  str:
    - rst
    - uvw
    - xyz

map:
  - key0: 0
  - key1: 1
  - key2: 2
  - $$: ignored
  - $$tail: ignored