Also, when is the thumb rule for creating new versions? If I fix a typo in a comment, should I increment the version number? I'm guessing no. But when should I?

You should definitely increment the version number on every release, as many things will depend on that (CPAN, users of your module that require a specific version, and the general confusion that comes from having two different releases with no good way of keeping them apart). Then, consider whether you need to make a release if all you did is change a code comment.

Things are of course different for modules that are just for internal consumption, in that case the only person the version numbers will have an importance for is you, and you can do things as you like. But since keeping good version numbering is important for any code that goes beyond yourself, it's a good habit to get into.