Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.3)
// Compass (v1.0.0.alpha.18)
// ----

@mixin trbl($width: null, $height: null, $parent: null) {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  width: $width;
  height: $height;
  margin: auto;
  @at-root #{$parent} {
    position: relative;
  }
}

.tbrl {
  @include trbl(100px, 50px, ".tbrl-wrapper");
}

SassMeister-output.css

.tbrl {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  width: 100px;
  height: 50px;
  margin: auto;
}
.tbrl-wrapper {
  position: relative;
}

SassMeister-rendered.html

<div class="tbrl-wrapper">
  <div class="tbrl">＼TBRL／</div>
</div>