Thanks for providing the clarification.

I can understand avoiding CPAN modules that require additional (non-Perl) libraries, have complex dependencies, or even those that need a C compiler to handle XS code. Beyond that, I wouldn't not use a CPAN module simply because it's not core.

Ref::Util will use XS code if a C compiler is available; otherwise, it falls back to pure Perl (see the last dot point in the DESCRIPTION). Other than that, it only has a handful of core module dependencies (see its Makefile.PL).