perldojo.org definitely. Gives a feeling of a place you can learn in a "disciplined" way and at the same time mens sana in corpore sano
That's good, but caveat: that latin phrase is often misquoted, as the Wikipedia's entry which you linked rightly asserts: "the original connotation of the phrase is that health of mind and body is good in itself and something to be rightly desired, as opposed to beauty, wealth, or power." More precisely Juvenal is making fun of those who pray for those other things and claims that only the former should be asked for.
In fact, it may be a forced analogy, but we could make the above recommendation into Perl development: just make your software healthy in the mind (algorithms) and in body (the way they're implemented). Do not mind beauty, wealth (cool code that only you can understand and that you stuffed there just to show how much of a guru you are) or power (premature/micro optimization). Of course there's a limit, since what I consider sane code has to be beautiful as well, notwithstanding the fact that Perl's deepest nature lies in the realm of pragmatics. Perhaps beauty should simply follow naturally and not be obsessively searched for.