(The 'perl Makefile.PL' step generates the xs file.)
It does not. The Makefile thereby generated has a rule that turns the supplied .pd file into .pm and .xs files, and for distributions that have "opted in" and with a PDL 2.058+, a .c file per operation (allowing parallel builds).

Probably the best heuristic to spot a PDL distro that generates XS rather than being a pure-Perl user of other PDL modules is the use of PDL::Core::Dev, and/or calls to pdlpp_stdargs.

In reply to Re^2: How to know if a CPAN module uses XS by etj
in thread How to know if a CPAN module uses XS by bcarroll

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