gmp_copy#
Return an independent copy of $x.
Because Math::GMP values are references to heap-allocated
mpz_t structures, two Perl variables can share the same
underlying integer. For the overloaded arithmetic operators that
does not matter — they always allocate a fresh result. If you
are about to call an in-place mutator (currently just
add_ui_gmp) and want to keep the original intact, copy first.