WWLD? (What would Lodis do?)
From the sounds of things they are not expecting you to write perl programs on the first day. It sounds more like they want to see what you know and if they would consider you trainable.
I would make sure I know my way around the command line. Many (read: almost all) linux support channels revolve around ssh sessions and you will need to know how to navigate. I don't mean type all paths from the root i.e. /home/me/dir1/dir2, etc... Learn to be comfortable with relative paths. if you need to copy a file from the parent directory just use "cp ../filename ." don't type out the full path to everything; knowing how to use relative paths is one thing that shows you have an understanding of how the command line environment works and is structured.
Pick your favorite text editor and get good with it in a terminal window. Nano, Pico and the like are fine as long as you know the weaknesses of them and understand that they are not part of every installation. Vi or Vim has a pretty steep learning curve but the advantage is you can find one or the other on almost every distro by default.
Understand devices /dev/ttyX, /dev/ttysX, /dev/srX, where X is the instance. Don't worry about how to configure and setup but know what they are used for in general. Oh yeah, learn and love the 'screen' command.
Compiling software and fixing dependencies is also going to be important but probably not the main focus of a skills eval.
Get familiar with sed, grep, mv, cp, cd, ls, tr, tar, and any other common scripting tools. Don't just know the names and what they mean, learn the switches and when to use them. No one wants you to open a man page every 5 seconds to look up the switch to make the grep case insensitive or to see what the syntax for the cut command is.
Beyond that, a good general knowledge of what the /var, /etc, /usr, /, /boot, /bin, /sbin, /proc, and /sys are all used for would be mandatory. you start installing compiled software to /proc and I think the test would be over.
Know how to control runlevels and where to start/stop/restart services. Not just using the Red Hat 'service' command but know how to go into /etc/init.d and do it there.
This is what came off the top of my head and in no way should be used as a study guide or be considered a complete collection of everything an entry level Linux support tech should know.
Lodis, I definitely appreciate the advice, but this has nothing to do with my recent job interview invitation. I'm looking for blog articles to go between "I just learned the terminal basics" and "Now I'm learning how to manage Linux servers." Things that aren't very admin-type tasks, but the kind of things an advanced user might know.
(I'll keep what you wrote for some google and wiki reading later today though!