There's nothing shell scripts can do that cannot be done in Perl¹. But there are things that are easier done in a shell script than in Perl. Sourcing other shell scripts for instance (and hence, getting access to environment variables). You can't really beat

  . /path/to/config/file
[download]

in Perl for ease, neither keystrokes.

¹Of course, there's nothing a Perl program can do that cannot be done in Python, Java or C. That doesn't imply some people rather write Perl...