You may be interested in our extensive collection of Axe Parser Tutorials:
http://www.omnimaga.org/index.php?action=articles;cat=12
Browse around there, there really is a whole bunch of useful stuff.
Also, be sure to check out the Axe Documentation.pdf file, the Commands.html file, and stuff like that. The commands.html file isn't so thorough, but it explains all the commands you can use, and gets you started so you can experiment with test-like programs to really figure stuff out. I remember reading about r1-r6 in Commands.html and thinking, uh, what? But it was all I needed to know to experiment and figure out what it meant.
Good luck :)
EDIT: Also, in case you don't already know, r1-r6 are found by pressing [vars][3] or something like that.