<===> input.scss
$foo\bar: 1;

@function foo\func() { @return 1; }
@mixin foo\mixin() { mixin-value: 1; }

.test {
    var-value: $foo\bar;
    func-value: foo\func();
    @include foo\mixin();
}

<===> output.css
.test {
  var-value: 1;
  func-value: 1;
  mixin-value: 1;
}