When should you use compilation with -Wc or just simple -c ?

My rule of thumb is, 'all the time, unless I have a very good reason not to'. My editor is set to automatically insert

use strict;
use warnings;
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automatically for every new Perl file I create. As you're running 5.8, I'd recommend doing the same - I can't count the number of times that a warning has caught me doing something stupid.

How can I resolve this problem, is there something wrong with Smart::Comments?

I've just copied your code and both checked and run it with no errors or warnings, so the problem is likely to be some misconfiguration or corruption with your setup. Unfortunately, I have no concrete idea of where the problem is likely to be. I'd guess that you possibly have a dependency problem with another module (either missing totally, or a version incompatibility). Given the content of the warning, I'd start by looking at your installation of version, as that's one of 5 direct dependencies for Smart::Comments

Hopefully someone with more clue and/or coffee in them will be along with a better answer soon - good luck