Here is some really good homework:

https://metacpan.org/source/BDFOY/PerlPowerTools-1.016/bin/cat

When I type man which at osx it says:

HISTORY
     The which command first appeared in FreeBSD 2.1.

AUTHORS
     The which utility was originally written in Perl

Reinventing wheels is great fun and practice. You never know "which" next great utility will be originally written in Perl! :) Keep on Truckin'