I think these figures also depend a lot on how many users have experience with a certain language, so a "useful" language with a small user base will likely get less vote.
For example, when it comes to Shell programming, I use a lot bash and zsh, and find zsh much more useful, simply because it contains many more (useful) features. Still, zsh isn't shown on top of the list - perhpas because many more users are exposed to bash first, and hence don't bother to learn a second shell programming language.
Aside from this, putting bash and Perl into the same boat for "scripting" tasks is a bit like comparing apples and oranges, not the least because "scripting" is such a foggy term. I use both (plus Ruby and, occasionally, Python), and I feel that it helps a lot if you know at least one shell (bash, zsh, ksh) PLUS one higher level language (Perl, Ruby, Python, ....).
As long as you do "only" simple tasks for automating routine jobs (which is what probably could be understood by the word "scripting"), it is a very academic question which one is "better". I have an slight inclination for the combination zsh/Ruby, but feel completely comfortable doing my job in bash/Perl too, because the differences between them are small.
Ronald Fischer <firstname.lastname@example.org>