There is no such thing :) http://search.cpan.org/~mbarbon/ExtUtils-XSpp-0.1602/lib/ExtUtils/XSpp.pod#OVERVIEW says

XS++ is just a thin layer over plain XS, hence to use it you are supposed to know, at the very least, C++ and XS.

So read the perlxstut, whatever c++ tuts, then follow the examples, that come with http://search.cpan.org/dist/ExtUtils-XSpp/MANIFEST, and the other ones