<===> input.scss
$map1: ( red: 'literal', transparent: 'literal' );
$map2: ( 'red': 'quoted', transparent: 'quoted' );
$map3: ( #{re}#{d}: 'interpolated', #{trans}#{parent}: 'quoted' );

foo {
  content: inspect($map1);
  content: inspect($map2);
  content: inspect($map3);
}

$merge1: map-merge($map1, $map2);
$merge2: map-merge($map1, $map3);
$merge3: map-merge($map2, $map3);

bar {
  content: inspect($merge1);
  content: inspect($merge2);
  content: inspect($merge3);
}
<===> output.css
foo {
  content: (red: "literal", transparent: "literal");
  content: ("red": "quoted", transparent: "quoted");
  content: (red: "interpolated", transparent: "quoted");
}

bar {
  content: (red: "literal", transparent: "quoted", "red": "quoted");
  content: (red: "literal", transparent: "literal", red: "interpolated", transparent: "quoted");
  content: ("red": "interpolated", transparent: "quoted", transparent: "quoted");
}