Thank you for you hint with Devel::AssertOS.

I looked into it, but I´m afraid it does not quite serve my purpose.

As I understand it dies when the underlying OS is not the intended one, but I covered that aspect already.

perl Makefile.PL # Maybe some option here? os=all|Linux|AIX|RHEL|Suse
make             # To get everything or things covered with option
                 # And if option is not possible:
make Linux       # To get Base plus all Linux stuff
make RHEL        # To get Base plus Linux.pm plus RHEL.pm
make Suse        # To get Base plus Linux.pm plus Suse.pm
make AIX         # To get Base plus AIX.pm
make test        # To test all related tests
make install     # To install only selected modules
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That way only the selected modules get installed out of my manifest.

As I see it, I must teach somehow Makefile.PL either to select the appropriate things I need when I call it (with options) or to make Makefile.Pl make additional targets (like AIX, Linux ...).

I saw the CONFIGURE attribute in the documentation of ExtUtils::MakeMaker which looked very promising to accomplish this:

CONFIGURE

    CODE reference. The subroutine should return a hash
    reference. The hash may contain further attributes,
    e.g. {LIBS => ...}, that have to be determined by some
    evaluation method.
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I also found a small article in CPAN how to create own make targets:

sub MY::postamble {
    return <<'MAKE_FRAG';
    $(MYEXTLIB): sdbm/Makefile
    cd sdbm && $(MAKE) all
    MAKE_FRAG
}
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But all that I find extremely vague and unintuitive...

A good example could help :-)

I looked into it, but I´m afraid it does not quite serve my purpose.

Look up :) AssertOS is in the CheckOS distribution ... Devel::CheckOS - check what OS we're running on ... this mean it doesn't die

So then

package System::Scaller;
use Module::Load qw/ load /;
use Devel::CheckOS qw/ os_is /;
my @targets = (
  [qw/ AIX  System::Scanner::AIX  /],
  [qw/ RHEL System::Scanner::Linux::RHEL  /],
  [qw/ SUSE System::Scanner::Linux::SUSE  /],
);
for my $targ ( @targets ){
    my( $name, $module ) = @_;
    if( os_is( $name ) ){
        load $module;
        @System::Scaller::ISA = $module;
        last;
    }
}

1;
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You install everything, you only load the module thats appropriate for the platform

Hacking Makefiles and only packing certain files is PITA, avoid it