using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var text = @"\firstcommand{\secondcommand{nestedcontent} outercontent}";
    	var pattern = @"\\(\w+)\{([^{}]*)}";
    	var prev = string.Empty;
    	do {
    		prev = text;
    		text = Regex.Replace(text, pattern, "<$1>$2</$1>");
    	} while (prev != text);
    	Console.WriteLine(text);
	}
}

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