.exclamation {
  // `!` is technically not allowed at the top-level of a custom property, but
  // that's only because `!important` is filtered out before the custom property
  // is parsed by the CSS parser. As far as Sass is concerned, it's fine.
  --important: value !important;

  // We even allow constructions like these for forwards-compatibility with
  // additional flags or syntax CSS might add.
  --multiple: !important !important;
  --other-word: !something;
  --in-identifier: foo!bar;
  --just-exclam: !;
  --just-exclams: !!!!!!!;
}