I had written (in C) a tricky but widely-appreciated utility, classify
It would compare a large group of files and tell you which ones were identical
(I used to to manage config files on a cluster of diskless workstations)
At 1992 USENIX, I showed it to someone
He said "Oh, you should have written this in Perl"
I didn't know Perl, so I couldn't argue with him.
So I learned Perl in order to prove he was wrong
But he was right