Two times I can recall using them in real life were for parsers to identify MIME and CSV files. I thought it was pretty elegant, but zoom forward a few years,

Two times I can recall using them in real life were for parsers to identify MIME and CSV files. I thought it was pretty elegant, but zoom forward a few years, and I got to listen to the new guy tell everyone in scrum how he had to fix a bug in there and it was all, ugh, *weird*.