Don't mind me, just a caffeinated ramble.
I think there's simple, there's efficient and there's idiomatic. Simple code is readable by nearly anyone with a general grasp on programming. Efficient does the task with the most efficient use of whatever resources are important to that task. Idiomatic code takes advantage of language features to clearly express an idea more succinctly. Idiomatic code is probably less readable to an unexperienced Perl dev, but perhaps more readable for the enlightened. Because performance is rarely an issue for the code I write, I usually shoot for simple and/or idiomatic and shuffle the code that must be unclear for the sake of efficiency into the dark corner of some library.
My guideline is that clever code is none of the above. Okay, really good clever code may be efficient, but it usually isn't. Most of the clever code I've come across is little more than exploring language features. "Did you know you can do X in Perl?" That's great at home, but I restrict my production code to the idioms I'm most familiar with. Yes, my old production code was simplistic to the point of irritation. Yes, some of my new production code would make a Perl novice twitch while still having simplistic spots that might irritate a guru. But I'm fairly confident that today I could go back and fix a bug in any of my production code. The coders who produced that "clever" code I hate probably couldn't. They've moved on to other features or other languages and probably couldn't even remember why that class needed operator overloading which was so sensitive to calling context or why they had to write the half the logic in an evaluated regular expression.
There's nothing wrong with being clever. It's fun and you learn from it. But I think we use "clever" as a pejorative when it looks like the original dev was just going "look what I can do!"