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CSharp · Console

/Program.cs

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;
					
public class Program
{
	public static void Main()
	{
		var input = @"<Hello> [World]!";
        var regex = new Regex(@"(?<=\<).*(?=\>)|(?<=\[).*(?=\])");
        var index = 0;
        var replacements = new List<string>();
        var formatString = regex.Replace(input, (m) => 
        {
            replacements.Add(m.Value);
            return String.Format("{{{0}}}", index++);
        });
        
        Console.WriteLine(formatString);
        Console.WriteLine(String.Join(Environment.NewLine, replacements.Select((v, i) => i + ": " + v).ToArray()));
    }
}