Here are the changes in the formula language in Ultra Fractal 6:
Perturbation equations
Fractal formulas can now contain perturbinit and perturbloop sections to provide equations for perturbation calculations (faster deep zooming). There are new #dz and #dpixel predefined symbols, and a new perturb setting. See Perturbation equations.
Miscellaneous
The compiler now always defines the symbol VER60. See Compiler directives.