*    *Assignments*

             +=  -=  *=  /=  %=  **=  <<=  >>=  x=  .=
             &=  |=  ^=  &.=  |.=  ^.=

         [snip]

         The subroutine for the assignment variant of an operator is
         required only to return the result of the operation.

##</code><code>##

void overload_add_eq(pTHX_ SV * a, SV * b, SV * third) {
     dXSARGS;
     PERL_UNUSED_ARG(third);
     mpz_add_ui(*(INT2PTR(mpz_t *, SvIVX(SvRV(a)))), *(INT2PTR(mpz_t *, SvIVX(SvRV(a)))), SvUV(b));
     XSRETURN(1);
}

##</code><code>##

void
overload_add_eq (a, b, third)
	SV *	a
	SV *	b
	SV *	third
        CODE:
        overload_add_eq (aTHX_ a, b, third);
        XSRETURN(1);