Generated by SassMeister.com, the Sass playground.

SassMeister-input.scss

// Sass v3.2.5

@mixin debug-outline($color: red, $background-color: false) {
  outline: 1px solid $color;
  @if $background-color != false {
    background-color: $background-color;
  }
}

.foo {
 @include debug-outline();
}
.bar {
  @include debug-outline(green, $background-color: yellow);
}
.baz {
    @include debug-outline(purple);
}

SassMeister-output.css

.foo {
  outline: 1px solid red;
}

.bar {
  outline: 1px solid green;
  background-color: yellow;
}

.baz {
  outline: 1px solid purple;
}