In my experience, as I've bettered my skills in Perl, I find that beautiful code is code that is efficient and elegant. The better a person tends to be at figuring out the best approach to a problem, the better that person tends to associate beauty and art in code with the skill and elegance involved in crafting it.

How many times have you seen a small snippet of code and thought to yourself, "Fuck, man, that's beautiful."?

Naturally there's going to be exceptions; nobody is a perfect coder, but I suspect this subconscious tendency only grows more accurate the better your skills are with a language.