Like ichimunki, I won't really say much beyond style, and in particular, deep nested conditionals.

As one example of reducing the complexity of your nesting (but different than ichimunki's suggestion of using logical operators), here is an alternate version of the foreach loop found within the getintnames() routine -- your loop was 26 lines long and 4 levels deep (with a couple of unnecessary indentations added as well).

foreach my $fpc (@lines) {
    if ($fpc =~ /Slot (\d+?).*$/) {
        $slotcounter = 1;
        $slot = $1;
        next;
    }
    next unless $slotcounter eq 1;
    next unless ($cardtype, $pic) = $fpc =~ /PIC (\d+?)\s+(.*?)\,.*$/;
    next unless $cardtype =~ /$type/;
    ($ports = $cardtype)  =~ s/^(\d)x.*/$1/;
    push @cardz, "so-$slot/$pic/$_" for 0 .. $ports - 1;
}
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Note, I removed your $knownthing variable altogether as you didn't really do anything with it. Also note, I can't really test the above for errors beyond syntax, so for that reason just consider it model rather than a plug-in alternative.

And a final note: my point was not to reduce the size of the loop, that was only a side-effect of reducing the nesting. However, some people frown at multiple points of escaping a loop iteration (though in this case the nested ifs amount to the same thing), so tmtowtdi and ymmv.