Yep, interesting, do you remember the initial text structure and operatins you would perform on it ?
There were three specific files that needed to be edited. Firewall rules were setup in pf.conf. IP-related configuration was controlled in both rc.conf and sysctl.conf.
There was also some issue with the difference between GNU sed and BSD sed having to do with the ability to make in-place edits with the -i option.