Salve Magister :-)
I just want to note some quick points. This is no very deep wisdom or something it all comes to you when you a) really think about this and/or b) got some experience in teaching coding. Plus I should note, that I'm surely not a coding wizard, I just get things done one or the other way ...

The most important thing is to pick up the students where they are.
(Masem already noted this in a way.) You should have a look at the code your student wrote in VB and you need to estimate his skills. Probably one could formalize this with a checklist you could got through which would contain points like

• Does he use for-loops only or does he mix different kinds of loops
• does he use "real" data structures like hashes or is he more the "keep 3 arrays synced"-type

or something like that, but I'm definetley not the one to create this list. If you got a feeling for his skills you'll find the things to teach easier. Often people can learn a new language just from the differences to the languages they already know.

Then you might be happy that you're going to teach perl, because you can stay with the language itself and don't need to introduce the compiler or other ugly stuff.

Do you already have some typical quests in mind he will be doing? Well, then just teach those little tricks first. I have found that most people need the

open(IN,"foo") or die "blah\n$!";
while(<IN>) {
  do_something_with_perls_special $_;
  ($probably,$they,$want,$to) = split(/;/);
  $probably =~ s/$change/$somestring/g;
  perform_some_test() and print "The Result\n";
}
close IN;
[download]

..-Stuff for the first days (or maybe weeks).

The Camel is not only full of knowledge, it's also really _fun_ to read. I made good experiences pointing that out. Though this may not count for an already experienced programmer.

I once managed to teach a 16-year old school girl (who was good at maths but had no computer experience at all) a little perl coding (including the shell basics and some XEmacs) in just three days. At the end of the third day she was programming a little adress-database (yeah, flat file, but HEY! ... ;-) inluding regexp querys!!

Well, then... Best wishes, all success (you won't need to luck ;) and happy teaching...

Regards...

Stefan