<===> options.yml
---
:todo:
- sass/libsass#2987

<===> input.scss
$red: red;
$foo: red;

:root {
  --red: #f00;
  // --red: $red;
  // --red: $foo;
}

a { content: var(--red) }
a { content: var(--$red) }
a { content: var(--$foo) }

b { content: (- red) }
b { content: (- $red) }
b { content: (- $foo) }

c { content: (+- red) }
c { content: (+- $red) }
c { content: (+- $foo) }

d { content: (-red) }
d { content: (-$red) }
d { content: (-$foo) }

e { content: (+ red) }
e { content: (+ $red) }
e { content: (+ $foo) }
<===> output.css
:root {
  --red: #f00;
}

a {
  content: var(--red);
}

a {
  content: var(-- red);
}

a {
  content: var(-- red);
}

b {
  content: -red;
}

b {
  content: -red;
}

b {
  content: -red;
}

c {
  content: +-red;
}

c {
  content: +-red;
}

c {
  content: +-red;
}

d {
  content: -red;
}

d {
  content: -red;
}

d {
  content: -red;
}

e {
  content: +red;
}

e {
  content: +red;
}

e {
  content: +red;
}