You are not going to get by as a Unix Administrator without learning shell scripting, you will find shell scripts through-out the system, some quick examples- crontab uses shell syntax, the systems /etc/init.d and /etc/rc?.d (or equivalent) scripts are written in shell. You will get install programs and wrapper programs written in shell and unless the systems are brand new and you are the only adminsitrator there will be shell scripts other people have written which you will have to maintain. Shell syntax is mandatory for the command prompt which is where you are going to be living most of the time if you stay in this work.

The good news is that you don't have to stop learning Perl whilst you develop your shell expertise and a great deal of what you learn in shell will be directly or almost directly translatable into Perl, Perl after all began life as an "assembly" of Unix shell tools. Learning Unix shell scripting can only help your Perl and learning Perl won't hurt your shell scripting - though it will spoil you a little :)

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Until you've lost your reputation, you never realize what a burden it was or what freedom really is. -Margaret Mitchell