“I'll second this motion.” Here's why...

It is a very instinctive thing, for a programmer, to look at a problem and to immediately consider how he would solve it. (And even, to consider it and then struggle with it for a little while and then post the question to PerlMonks.)

It is not so instinctive to stop and ask oneself: “hasn't this already been done by someone else?”

And so you overlook things like List::Compare, and List::AllUtils, simply because it never occurred to you to look for them.

Mind you, I do it too! We all do. Schools teach you that “everything you do must be your own work,” and they stick you in semester-long classes where you monkey-around with manual manipulation of data structures, in various inexcusable languages. Before that, generations of programmers worked in an environment where “an instantaneous and vast online code resource” did not exist ... the closest thing we ever had were SHARE tapes.

When you leverage existing code like this, it's not only quite-a-bit more descriptive of what your code is actually doing, but it pushes the “how” aspect out-of-sight out-of-mind. Your code simply posits that an existing block of tested code to do this thing already exists, and uses that code to do it. While it could be debated, endlessly of course, whether such a herculean travesty is or is not “efficient” for the computer, it sure is efficient for you.