(1) Perl is not taught in colleges for the same reason that other interpreted
languages are not: they are poor choices for teaching fundamental programming
techniques and OS manipulation (memory manipulation, I/O, etc.). This is not to
say that such languages shouldn't be taught at the college level -- just that
traditional CS programs are more likely to stick with what they know and can
teach a student in four years.
As noted in other replies, a solid programmer in any language -- such as those
actually taught in colleges -- can likely be introduced to perl and become
proficient in a matter of a week or two.
(2) I'm not sure where you're coming from, but the buzz word 'CGI' never implied
perl to me. It implied a dynamic site that was using any of a number of
languages behind the scene -- C and perl being most common, but not the only
players on the block (I saw sites written in shell).
(2a) Regarding CPAN, it's not just about the central, searchable repository;
it's also about the fact that CPAN: is a distribution mechanism that tracks
dependencies; provides a testing framework; provides nightly builds of
documentation; and more.