Learning HAL and external offsets

Hello,I have a project where I want to apply changes to a cnc toolpath in realtime based on object tracking data from a camera. I have been told that while uncommon, that it is possible. Particularly, to use a hardware abstraction layer to apply external offsets so that the original g-code remains unchanged and the toolpath can still be updated. However, as a novice and having done a deep dive into this topic, I find it very difficult to complete this project because of the lack of information on these topics. Can anyone direct me or recommend how I can learn how to use HAL and external offsets? I have also been suggested that parametrized g-code is dynamic and can work. That Fanuc controls have a feature called real time macro and Siemens controls have a feature called parallel program execution, which I may be able to code in linuxcnc. Thanks!

Regarding HAL see section 'HAL (Hardware Abstraction Layer' :
linuxcnc.org/docs/stable/html/

Regarding External offsets:
linuxcnc.org/docs/stable/html/motion/external-offsets.html