$orig: 0.12em;
$value: (0.12em);
$score: (item-height: 0.12em);
foo {
    tst-1: 0 -#{0.12em};
    tst-2: 0 -#{$orig};
    tst-3: 0 -#{$value};
    tst-4: 0 -#{map-get($score, item-height)};
}