When you write any documentation you have to assume some level of information that the future reader might have on the subject. Obviously this is not only a problem with Perl.
My first comments are nearly useless to me now (or just plain stupid). But on the other hand those scribblings are self-documenting because they are that simple. Nowadays, though I am far from beeing really good, I want to include pod in my code and when I think the code may be used or reviewed by a complete novice I add comments of the redundant form.
 
I wrote I want to, but it still is an excercise in self discipline. It is far quicker to just enter a few comments.