String replaceFirstMapped(Pattern from, String replace(Match match), [int startIndex = 0])

Replace the first occurence of from in this string.

Returns a new string, which is this string except that the first match of pattern, starting from startIndex, is replaced by the result of calling replace with the match object.

If the value returned by calling replace is not a String, it is converted to a String using its toString method, which must then return a string.

Source 

String replaceFirstMapped(Pattern from, String replace(Match match),
                          [int startIndex = 0]);