Many resources: http://pangaro.com/definition-cybernetics.html
That seems false. PID is used all over, no models. Very simple, very effective.
I guess it's somewhat more true in programming, because if you have only ten lines, can you even call it modeling?
That said, I like to say that the best kind of code teaches you something new abou the problem it's solving. Some invariant, widely usable simplification, etc. Still not the same as modeling the system as such, though.
Ten? Do you even Perl?
Either the authors made rudimentary error or they specified the context. If you read forward, they define the problem and discuss error and cause controlled regulation.
If one can't make the connection between Turing completeness/automata theory and Neuro-cognititive function...think more.
