I have met many advanced perl programmers who still dont use things like map, binary operators, tied hashes, who are afraid of globs, toying with references, multilevel datastructures, and so on.
I have to question this statement. What makes a programmer "advanced" with regard to a language but familiarity and experience with all or most of a language's features? I would have a hard time judging a perl programmer as advanced if he didn't use map or binary operators and was "afraid" of globs but one that didn't use complex data structures wouldn't even be "intermediate" in my book.
To answer your question though, I would be grateful for some training in Perl internals and Perl/C integration. I know both languages well. I've written a couple simple XS modules and I even managed to embed perl in another application once (though I chose the easiest possible way to do it.) Still, I have found my excursions into those areas to be slow going. I've basically bumbled through my attempts. An instructor would help immensely, I imagine.
"My two cents aren't worth a dime.";