What point are you trying to make though?
My point is that the OP's list of reasons "why perl" aren't very good reasons, because they mostly don't separate perl from the herd of other languages. "It's what I know and so it's what I can teach" is, however, an excellent reason for teaching in perl, provided that the desired end point isn't "the students know perl" but "the students know a dynamic language" or something like that.
They can then use their new knowledge of programming (gained via the medium of perl) in whatever similar language they find is most appropriate for the task at hand. IME the choice of which language is most appropriate is hardly ever determined by technical or linguistic matters, but by what your colleagues are most familiar with and what they've already got code written in. Taking my current job and task as an example, the best language from a technical PoV would probably be something like SML or Haskell, because I'm constantly getting my arse kicked by data type problems. But the rest of the application has already been written in perl, by perl programmers, so the best language from the social PoV (which is more important than the technical PoV) is perl.