I suspect there may be a different lesson in here. Let's take another look at what you wrote.

My supervisor, who is a good perl programmer himself, asked me if I knew of a way to count the keys in a hash. 'Sure,' I replied and wrote down $#{[keys(%hash)]}+1.

He studied it for a moment or two, said 'ugh' and wandered off shaking his head in disgust.

People say perl is unintelligable..... for the life of me I cannot see why ;)

I was wondering if anyone had a similar story... how the use of a little syntactic gibberish has led to feelings of wonder/amazement/disgust in others (delete as appropriate).

Without significant contortion of meaning, this can be rewritten as

By supervisor, a good perl programmer, studied my syntactic gibberish, said 'ugh' and shook his head in disgust.

Looked at this way, I would suspect that his comment might have been less about Perl than it was about your overcomplexifying what should have been a simple.

Projecting a bit of my experience into this, a chronic problem that some technical managers have is a tendency of some developers to make simple things complicated (perhaps for the sheer joy of it).

I recommend you have talk with your supervisor, and get clarity on what the 'ugh' was about.