using System;
using System.Text.RegularExpressions;
public class Test
{
public static void Main()
{
string pattern = @"(?<={{)\w+(?=}})";
string input = @"{{aaa}}";
foreach (Match m in Regex.Matches(input, pattern))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
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