. I am asking if there is a way, in CPAN metadata, to express that code expects $Config{useperlio} eq 'define' in the build of perl that is running the program,

Why? C-requirements are defined in .c and .h files not in CPAN metadata.

Which part of which file of your module depends on USE_PERLIO ( "perlio.h" )?

Why is it important for CPAN metadata to know about C-level requirements ?

Code in Build.PL/Makefile.PL is often used to check for missing .h or .c level dependencies. Some go a step further with Alien:: modules that install those dependencies.

You can add in Makefile.PL any check of %Config prerequisites

Devel::PPPort helps with compiling .xs modules on older versions of perl.h

or do I need to consider the "PerlIO not available" case?

Do you? Have you encountered a squeaky wheel that needs grease? cpantesters can help find squeaks

PerlIO is a module ... but does it depend on USE_PERLIO? (does it matter?)

In reply to Re^3: How to declare a dependency on PerlIO in a CPAN module? by Anonymous Monk
in thread How to declare a dependency on PerlIO in a CPAN module? by jcb

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