It's a great practice to have the trailing comma. Larry added it because he saw programmers add elements to a list (or whatever their language called it but forget the separator character. Perl allows the trailing comma to make that less common. It's not a quirk or side effect of something else. That's what Perl wants you to do.
What is bad practice, however, is distracting a meeting full of people with something your boss could have corrected later. Unless the meeting was specifically a code review, your boss wasted a bunch of time. I've always wished that to join a video conference, you had to enter your per-minute compensation so a counter would show on everyone's screen to show how much money was being wasted. Spending a couple hundred dollars watching you remove commas on a working program would tamp down that nonsense.
