File::Spec core module is comprised of submodules, one of which is File::Spec::VMS.
And it does use VMS::Filespec;,
but there is no VMS::Filespec module on any of my 3 machines: OpenBSD, Linux, Windows StrawberryPerl.
I've done full filesystem search to be sure

I don't actually need it, I just wanted to see VMS file path separators in action.
I tried editing File::Spec

# diff /usr/libdata/perl5/amd64-openbsd/File/Spec.pm{.original,} 
19c19
< my $module = $module{$^O} || 'Unix';
---
> my $module = $module{VMS} || 'Unix';
[download]

and then:

> perl -MFile::Spec -E 'say File::Spec->catfile( "", "" )'
Can't locate VMS/Filespec.pm in @INC ...
[download]

But it can't.
I also tried cpan VMS::Filespec but:

The most recent version "1.13" of the module "VMS::Filespec"
is part of the perl-5.36.3 distribution. To install that, you need to 
+run
  force install VMS::Filespec   --or--
  install PEVANS/perl-5.36.3.tar.gz
[download]

So it isn't installable as any regular module.
And if I force - cpan -f -i VMS::Filespec - it seems to be going to install perl-5.36.3.
which I haven't tried as it scary as it might break the system.

So,

• Why standard core module comes with missing parts?
• How do I install the missing part?