@dziban It is, indeed, just some rules. "Compilation" is concatenation of rule-sets.
The current implementation of Nova allows for an "escape hatch" in the form of patterns that are prefixed with a '%'.
For the current implementation, rules are parsed and compiled to a form of byte-code that incorporates a stack.
So..
%$variable = 1 2 +.
..results in a tuple that looks like..
$variable = 3
The new implementation will not feature this, as this was done for demonstration purposes.