learn the bash or ksh. unix has been around, umm, a long time and hasnt changed much. chances are, its going to be here quite a while to come.
you can earn $70k if you are a good unix admin, more if you write the scripts, at least in my neck of the woods, which is actually funny -there are so many unix jobs around my home, and I live 15 minutes from Redmond.
.net is a good bet, but that is going to change some day too, and probably before someone rewrites the bash.
Perl is pretty similar in some minor respects to what i mentioned above, without the history, well, not 30+ years of it at least, and Perl does get a overhaul from time to time, so it does change.