I didn't quite understand what you try to achieve so just a stylistic remark:

The inner while is useless, because after the first iteration it will always leave the inner while. You could write it this way instead:

for (3 .. 8) {
        my $pdu_num = $_;
        $pdu_num = 11 - $pdu_num unless defined $order;
        if (@nodes) {
                my $node = shift @nodes;
                $map{$node} = $pdu . '['.$pdu_num.']';
                next;
        }
}
[download]

Now you don't have nested loops anymore, so you don't need the label for next. (Actually you don't need the next at all, because it's the last statement in that loop)

Update: another slightly improved version:

for (3 .. 8) {
        my $pdu_num = $_;
        $pdu_num = 11 - $pdu_num unless defined $order;
        last unless @nodes;   
        my $node = shift @nodes;
        $map{$node} = $pdu . '['.$pdu_num.']';
}
[download]