What You Learned

Perl is really neat

Associative arrays
No need to declare variables
Can run external programs, and grab output, very easy
Lots of text processing features like split and chomp

There are lots of ways to mess up a Unix system

Password and shadow file should agree
Home dirs and mail spools must be checked
User disk usage should be checked.
Sometimes users just disappear. Their accounts should too.

Perl can help automate this stuff. Saves time for more useful things.
http://euclid.nmu.edu/~randy/Research/AccountCheck