Security's a good one, but AFAICT there isn't a good way to say "I know how to write secure code, and here are the credentials to back me up" unless you've spent some time on the OpenBSD audit team or something.

Personally, I think you're looking at skills from too low a level. If I hired someone for an even remotely lucrative position, I'd expect them to be able to pick up pretty much all of the above (except maybe security) in a week or two at the outside. I'd rather see that they can write solid code, have a good background in computing science (not the same thing as having a CS degree -- the two are so separate in my experience as to be completely orthogonal), and are interested in continual improvement.

Pick up a couple of other languages besides Perl. You shouldn't need to become expert in them: the point here is to broaden your experience and expose yourself to other ways of doing things. Do some CGI, some DBI, some systems programming... don't tie yourself down to one technique. (HR people seem to love advertising for very specific positions -- "Visual C++ 6.0/MFC 2.17 programmer needed" -- but any technical manager you're going to want to work for will be more impressed by a broad skillset than a passel of buzzwords.)

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