(Re https://github.com/sisyphus/math-gmpz/blob/master/typemap)
I don't think their(sic) identical. I believe that all occurrences of "$type" and "$var" represent separate, unique values.
Well they do once ExtUtils::ParseXS expands them. There's a reason they're in there as $variables. If you make that typemap read as just this: 
mpq_t *            GMP_PTR
mpz_t *            GMP_PTR
mpf_t *            GMP_PTR
mpfr_t *        GMP_PTR
gmp_randstate_t *    GMP_PTR

INPUT
GMP_PTR
            $var = INT2PTR($type, SvIVX(SvRV($arg)))

[download]
It still works correctly. (Yes, I just tried it) As a matter of fact, the Perl-supplied typemap includes an entry already that does the above, but better because it also checks the SV is a ref first: 
mpq_t *                 T_PTRREF
mpz_t *                 T_PTRREF
mpf_t *                 T_PTRREF
mpfr_t *                T_PTRREF
gmp_randstate_t *       T_PTRREF

[download]

In reply to Re^14: Puzzled by value of $overload::ops{binary} by etj
in thread Puzzled by value of $overload::ops{binary} by syphilis

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