How can I tell if a Perl module is core or part of the standard install?

How can I check if a Perl module is part of the core - i.e. it is part of the standard installation?

I'm looking for:

a command-line command:
a Perl subroutine/function to check within code

Perhaps the question should be: How can I tell what modules were originally provided with the specific Perl installation on a machine? (Actually, it is now asked as How can I tell what modules were originally provided with the specific Perl installation on a machine?.)

Given that there now appears to not to be an overall Perl standard installation, at least the answer to this new question will tell me what I originally had in the installation when it was first installed.

With that knowledge and if I keep the original installer image/package OR know how to get the exact thing again online, then I have a repeatable Perl installation for several machines with the knowledge of what modules will be present and what modules will not.

To clarify further: I am looking at what came with the installation originally, what modules were provided as part of that installation, and what was built-in. NOT what has been installed since then.

And I want to be able to do this on the machine that has the installation. So for this I would be relying upon the installation to have a record in some form as to what it has originally.

I asked spin-off question: How can I tell what modules were originally provided with the specific Perl installation on a machine? (How can I tell what modules were originally provided with the specific Perl installation on a machine?)

Solution

The corelist command from the Module::CoreList module will determine if a module is Core or not.

> corelist Carp

Carp was first release with perl 5

> corelist XML::Twig

XML::Twig was not in CORE (or so I think)

Here is one way to use it in a script. The Module::CoreList POD is too terse -- you have to go hunting through the source code to find what methods to call:

use strict;
use warnings;
use Module::CoreList;

my $mod = 'Carp';
#my $mod = 'XML::Twig';
my @ms = Module::CoreList->find_modules(qr/^$mod$/);
if (@ms) {
    print "$mod in core\n";
}
else {
    print "$mod not in core\n";
}

__END__

Carp in core