Congratulations on finishing the book and all its exercises! Now when you sit down thinking about what to do, some of your experiences on the exercises must have been plugged into your mind somehow, because that's what I believe exercising is for. It's designed to, among others, make you feel at home, or in your words, "felt my self familiar with perl".
in reply to FEAR OF PERL
Feeling familiar to me is more than enough to keep the fear far away, and start something. The only thing you need is really try it for youself. You already have the task, writing scripts to administrate a Linux box. Be more specific on a particular task, be sure to know what you really need to accomplish, step by step. Do you need to read lines? Do you need to extract some specific string from those lines? Do you have to show the output to the screen? Or, do you need to keep the result in a file? Whatever you need to do, I believe you already did most (if not all) of them. Just map them to the exercising you tried. And start typing.
If you get stuck, you know where to ask to. Before you do that, be sure to check relevant docs, right in front of you, with man or perldoc programs. It it's about subroutines, you can view man perlsub or perldoc perlsub. If it's about data or variable, perldata is there. If it's about a specific function, then perldoc -f function_name is available. And if you don't know what docs to read, start with man perl or perldoc perl.
Open source softwares? Share and enjoy. Make profit from them if you can. Yet, share and enjoy!