using System;

using System.Text.RegularExpressions;

public class Program

{

    private static string ConvertSuperscriptToText(Match m){

        string res = m.Groups[1].Value;

        res = "^" + res;

        return res;

    }

    public static void Main()

    {

        string expression = "2⁻¹² + 3³ / 4⁽³⁻¹⁾";

        string desiredResult = "2^-12 + 3^3 / 4^(3-1)";

        string supChars = "([¹²³⁴⁵⁶⁷⁸⁹⁰⁺⁻⁽⁾]+)";

        string result = Regex.Replace(expression, supChars, ConvertSuperscriptToText);

​

        Console.WriteLine(result); // Currently prints 2^⁻¹² + 3^³ / 4^⁽³⁻¹⁾

        Console.WriteLine(result == desiredResult); // Currently prints false

    }

}