pp.h:#define RETPUSHYES RETURNX(PUSHs(&PL_sv_yes))
pp.h:#define RETURNX(x) return x, PUTBACK, NORMAL
pp.h:#define PUSHs(s)   (*++sp = (s))
perlapi.h:#define PL_sv_yes             (*Perl_Isv_yes_ptr(aTHXo))

pp.h:#define NORMAL PL_op->op_next
pp.h:#define PUTBACK            PL_stack_sp = sp