Perl Style: Defensive Programming

use strict
#!/usr/bin/perl -w
Check all syscall return values, printing $!
Watch for external program failures in $?
Check $@ after eval"" or s///ee.
Parameter asserts
#!/usr/bin/perl -T
Always have an else after a chain of elsifs
Put commas at the end of lists to so your program won't break if someone inserts another item at the end of the list.