using System;

using System.Text.RegularExpressions;

public class Program

{

    public static string SafeReplace(string input, string find, string replace, bool matchWholeWord)

    {

        string textToFind = matchWholeWord ? string.Format(@"(?<=^|\s){0}(?=[$|\s])", Regex.Escape(find)) : Regex.Escape(find);

        return Regex.Replace(input, textToFind, replace);

    }   

    public static void Main()

    {

        Console.WriteLine(SafeReplace("Peter[='111222'] + APeter[='111222']",  "Peter[='111222']", "@", true));

        Console.WriteLine(SafeReplace("asd.len + hasd.len",  "asd.len", "@", true));

        Console.WriteLine(SafeReplace("Q5.count[=1] = 0 and hQ5.count[=1] > 0",  "Q5.count[=1]", "@", true));

    }

}