<===> input.scss
$Selectors: ();

//////////////////////////////
// Add selectors of various depths and makeups
//////////////////////////////
.foo {
  $Selectors: append($Selectors, &) !global;
}

.bar a {
  $Selectors: append($Selectors, &) !global;
}

.bar,
.baz {
  $Selectors: append($Selectors, &) !global;
}

.qux {
  &.waldo {
    .where & {
      .final {
        $Selectors: append($Selectors, &) !global;
      }
    }
  }
}

//////////////////////////////
// Display Results
//////////////////////////////
.result {
  length: length($Selectors);
  content: $Selectors;
  @for $i from 1 through length($Selectors) {
    index: $i;
    length: length(nth($Selectors, $i));
    content: nth($Selectors, $i);
  }
}
<===> output.css
.result {
  length: 4;
  content: .foo .bar a .bar, .baz .where .qux.waldo .final;
  index: 1;
  length: 1;
  content: .foo;
  index: 2;
  length: 1;
  content: .bar a;
  index: 3;
  length: 2;
  content: .bar, .baz;
  index: 4;
  length: 1;
  content: .where .qux.waldo .final;
}