Replaces matches using string.Remove().Insert()

LowLevelReplace.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace LowLevelReplace {
    class Program {
        static readonly Regex template = new Regex(@"({(.*?)})", RegexOptions.Compiled);
        static readonly Dictionary<string, string> values = new Dictionary<string, string>() {
            { "meow", "nya" },
            { "cute", "kawaii" }
        };

        class MatchesReverser : IComparer {
            public int Compare(object x, object y) => (y as Match).Index - (x as Match).Index;
        }

        static string ReplaceAll(string text) {
            var matches = new ArrayList(template.Matches(text));
            matches.Sort(new MatchesReverser());  // Replacing from end to beginning for not to mess 
            foreach(Match match in matches) {     // with indices while changing the original string
                text = text.Remove(match.Groups[1].Index, match.Groups[1].Length)
                           .Insert(match.Groups[1].Index, GetValue(match.Groups[2].Value));
            }
            return text;
        }

        static string GetValue(string key) {
            if(values.ContainsKey(key)) {
                return values[key];
            }
            return "[Unresolved]";
        }

        static void Main(string[] args) {
            Console.WriteLine(ReplaceAll("{cute} creatures say meow {meow} meow"));
        }
    }
}