Perl already knows your OS, $^O.

And are you kidding me with that if/else travesty?

If a small scale change, use a hash of subroutine references to make dispatching easy.

If you have time, create a parent class and subclass out to each OS (again, if you really have to do different things on each OS).

use strict;

my $os_dispatch = {
    linux   => sub {print qq{Linux\n}},
    solaris => sub {print qq{Solaris\n}},
    aix     => sub {print qq{AIX\n}},
    freebsd => sub {print qq{FreeBSD\n}},
    darwin  => sub {print qq{MacOSX\n}},
    unknown => sub {print qq{Unknown\n}},
};

if (exists $os_dispatch->{$^O}) {
    $os_dispatch->{$^O}->();
}
else {
    $os_dispatch->{unknown}->();
}
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Finally, do you really have to do that much OS specific stuff?