Having written a twenty+ page shell script that's in use all over my workplace, I can relate to his muse.

Were the question to be phrased, "If you had to choose just one existing language to serve all your needs, what would it be," I think he'd choose Perl too. You should also point out that his shell programs use a lot of tools that are not themselves written in shell script.

Ask him how happy he'd be without grep and awk! :D