TIL, as they say. This is completely valid C++ code, compiling without any errors.

#include <iostream>

int main() <%
    int a<:5:> = <% 1, 2, 3, 4, 5 %>;
    std::cout << a<:2:>;

    return 0;

It all has to do with so called di- and trigraphs. Of course I would not use these anywhere unless, somehow, absolutely necessary. No doubt it would only get people confused about your code.