I think the big problem (which is difficult to solve on Perlmonks, especally with new users) is knowing who you are trying to help.

Some people just need a little help: even if their style is different from yours it is not that bad, and a little hint (such as reminding/showing them how to print error messages) will be enough to get them to solve their problem and improve their skills.

Other people, while asking for an answer to a specific problem, show code that exhibits many more problems. To those I think it is worth mentionning the most glaring ones, along with again some hints, at least unless they show they belong to that last category...

...people who really don't get it, and who don't seem to be interested in improving their skills. They just want their ugly code to be fixed, or a canned script that solves the problem. Then it might still be worth explaining what's wrong, less for the original poster and more for others who might be reading the thread, but I admit that I often feel much less incentive to do so, as I know most of the advice is ignored by the person I am trying to help.

But really, thinking that you are not only answering one person but also helping many others who will be reading you, helps staying positive. And if you don't feel like it, you can always ignore the thread and let some other monk help... while you help someone else.