list.scss

$list: (black);
$list: join($list, white, comma);

div {
  padding: join(10px 20px, 30px 40px);
  margin: join((0, 10px), (10px, 10px), space);
  background: linear-gradient($list);
}

$list: ();
$list: join($list, (red, blue), comma);

p {
  background: linear-gradient($list);
}

$list: [];
$list: join($list, [red, blue], comma);

.bracket-list {
  background: linear-gradient($list);
}

div {
x: index(1px solid red, solid);
y: index(1px solid red, dashed);
z: index((width: 10px, height: 20px), (height 20px));
}

$list: set-nth($list: 10px 20px 30px, $n: 2, $value: -20px);
div {
    a: nth($list, 1);
   b: nth($list, 2);
  c: nth($list, 3);
 d: nth($list, -1);
}

div {
x:list-separator(1px 2px 3px);
y:list-separator(1px, 2px, 3px);
z:list-separator('foo');
}