Gross is designed as a daemon for configuring network, but is actually much more powerful than that.
First of all, you do not have to understand this section in order to use gross.
Gross was initially designed for network configuration. However, doing so turned out to be equivalent to implementing a light Domain Specific Language, entirely in Ruby.
This DSL is entirely based on the notion of backtracking: it successively runs commands, and in case any command in the already-started commands fails, all the dependent commands are deactivated and the failed command is started anew. If a command fails to initialize, it switches to the next non-dependent command and runs it ; until it manages to initialize the previously failed command.
This may sound hard to understand, but it is just under-the-hood management: you usually will just write declarative scripts and it will Just Work (TM).
At the moment not enough tasks are implemented, so it is just a toy language, not yet suited for production use.
So here is the usual Hello World:
g = Gross::Machine.new g.print "Hello World!\n" g.run
And here is a (slightly) more contrived example:
g = Gross::Machine.new var = g.set 'rand', ->(c) { rand(1..10) } g.print { |c| "Random number between 1 and 10: #{c.rand}" } << var g.run
Of course this does not make any use of backtracking, which is the power feature of this language, given there is no external state yet to trigger backtracking.