@function hello($name) {
    @return $name;
}

$foo: (
  bar() : baz,
  bar("foo") : blah,
  hello("bob") : bam,
);

a {
  foo: map-get($foo, "bar()");
  foo: map-get($foo, "bar(\"foo\")");
  foo: map-get($foo, 'bar("foo")');
  foo: map-get($foo, "bob");
}