Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.9)
// Compass (v1.0.1)
// ----

//Write mixins where the pattern takes variables
@mixin transparent-backgroung($color, $alpha) {
  $rgba: rgba($color, $alpha);
  $ie-hex-str: ie-hex-str($rgba);
  background-color: transparent;
  background-color: $rgba;
  filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#{$ie-hex-str},endColorstr=#{$ie-hex-str});
  zoom: 1;
}

.box {
  @include transparent-backgroung(black, 0.4);
}

SassMeister-output.css

.box {
  background-color: transparent;
  background-color: rgba(0, 0, 0, 0.4);
  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#66000000,endColorstr=#66000000);
  zoom: 1;
}