1 + 1 = 3

Ruby.
Classes are open.

class Fixnum
 def + x
   - (- self - x - 1)
 end
end

p 1 + 1 

C#...

static class Program
{
   static void Main(string[] args)
   {
       Console.WriteLine("1 + 1 = {0}", 1 + 1);
       Console.ReadLine();
   }
}

public class Console
{
   public static void WriteLine(string format, object arg0)
   {
       if (arg0 is int)
       {
           arg0 = (int)arg0 + 1;
       }

       System.Console.WriteLine(format, arg0);
   }

   public static string ReadLine()
   {
       return System.Console.ReadLine();
   }
}