Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

@function at2x-name($filename) {
  $length: str-length($filename);
  @if $length == 0 {
    // return empty if input is empty
    @return $filename;
  }
  
  @for $i from str-length($filename) through 1 {
    $slice: str-slice($filename, $i, $i);
    @if $slice == "." {
      @return str-insert($filename, "@2x", $i);
    }
  }
  
  @return $filename + "@2x";
}

.test {
  content: at2x-name("");
  content: at2x-name("test");
  content: at2x-name("test.png");
  content: at2x-name("test.abc.png");
}

SassMeister-output.css

.test {
  content: "";
  content: "test@2x";
  content: "[email protected]";
  content: "[email protected]";
}