Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.1)
// Compass (v0.13.alpha.10)
// ----

// String replace function
// @param $string: string to replace in
// @param $old: string to replace
// @param $new: string to replace $old into
// @param $case-sensitive: case sensitiveness
@function str-replace($string, $old, $new: '', $case-sensitive: true) {
  // Checking for arguments accuracy
  @if type-of($string) != string or type-of($old) != string or type-of($new) != string {
    @warn "One of the 3 arguments is not a string.";
    @return $string;
  }
  
  // Prevent from infinite recursion
  @if str-index($new, $old) != 0 {
    @warn "The string to be replaced is contained in the new string. Infinite recursion avoided.";
    @return $string;
  }
  
  // Checking for case 
  $index: if(not $case-sensitive, str-index(to-lower-case($string), to-lower-case($old)),  str-index($string, $old));
  
  // Doing anything only if $old has been found
  // And if new is different from old
  @if $index > 0 and $new != $old {
    $new-string: quote(str-slice($string, 1, $index - 1));
    @for $i from $index through str-length($string) {
      @if $i < $index or $i >= $index + str-length($old) {
        $new-string: $new-string + str-slice($string, $i, $i);
      }
    }
    // Going recursive
    @return quote(str-replace(str-insert($new-string, $new, $index), $old, $new, $case-sensitive)); 
  }
  @return $string;
} 

sass {
  $string: "There you go, Hugo!";
  replace: str-replace($string, "Hugo", "Nico");
  $string: "Second example with some more letters, especially the letter E.";
  replace: str-replace($string, "e", "z", false);
}

SassMeister-output.css

sass {
  replace: "There you go, Nico!";
  replace: "Szcond zxamplz with somz morz lzttzrs, zspzcially thz lzttzr z.";
}