%YAML 1.1
---
!!map {
  ? !!str "---"
  : !!str "foo",
  ? !!str "..."
  : !!str "bar"
}
%YAML 1.1
---
!!seq [
  !!str "---",
  !!str "...",
  !!map {
    ? !!str "---"
    : !!str "..."
  }
]