$map: (aaa: 100, bbb: 200, ccc: 300);

a {
  b: index($map, aaa 100);
  b: index($map, bbb 200);
  b: index($map, ccc 300);

  c: index($map, (aaa 100));
  c: index($map, (bbb 200));
  c: index($map, (ccc 300));

  d: index($map, (aaa, 100));
  d: index($map, (bbb, 200));
  d: index($map, (ccc, 300));
}