I pretend to be a sysadmin for my home system (Linux Debian). I totally disagree with the statement that Perl is the only scripting language that one needs to know as a sysadmin, because a sysadmin not only has to write his/her own scripts, he/she must be able to understand the code written by others, and much code one runs into while doing sysadmin work (at least in the Linux/Unix universe) is not written in Perl.
IME, I find that being able to understand bash scripts and have a clue about how to edit these scripts is a an absolute must in the Linux universe. Next in the list is C. After that it's a toss up between Python and C++, though Python is gaining the upper hand. (Just not to confuse anyone, I don't mean to imply that C and C++ are scripting languages; I'm just referring to the frequency with which I've had to be able to grok a non-Perl language in order to take care of a sysadmin task, irrespective of the specifics of the language.)