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

public class Test
{
	public static void Main()
	{
		var s = "{?:participants::lookup(.,{eeid},[[{catalog}]])}";
		var rx = @"(?<!\[\[)\{([^:{}]*)}(?!]])";
    	var res = Regex.Matches(s, rx).Cast<Match>().Select(x => x.Groups[1].Value);
        foreach (var t in res)
        	Console.WriteLine(t);
	}
}