What is really critical is to know
the whole menagerie:
$_ $, $. $; $@ and all their buddies
Sneer at users of English
Also, learn CPAN. Anything can be solved by exactly one page of code, if that code is written on top of CPAN.
Use zero-width assertions in your regular expressions. If you are just using the egrep subset, you are not a ninja yet.
Use defaults as if every keystroke cost you one drop of blood.