I agree that programmers should learn the 'Unix philosophy', but lumping Perl in there doesn't make much sense. Perl is just a scripting language, like Python or Ruby, and one of which I'm not particularly fond. It does not espouse 'one tool, one task' — "those days are dead and gone and the eulogy was delivered by Perl." Definitely learn shell, awk, sed, and co. But avoiding Perl won't do any harm.