Rabbit 0.2 Basics

I am trying to use Rabbit 0.2 and running into some difficulties
interpreting the basic inputs and outputs of some of the components,
specifically the LSystem and Turtle. I'm trying to figure out how to
define a variable related to a string(seed) to include in my production
rule (something as simple as A+1=A). Also, how the outputs from LSystem are
interpreted into specific geometries. Are there any tutorials or definitions available to share that would help in following data through the components? Any help appreciated...

PS The principles outlined in 'The Algorithmic Beauty of Plants' are pretty cool. Thanks morphocode for the work and links.