Undocumented Pan6 statements: oldselect, oldselectfewer, oldselectadditional, and logic

I am helping someone convert some Pan6 databases to PanX. I have found several statements that seem to work in Pan6, but do not appear in any of the documentation that I have. I think I have figured out what they are doing, but would still like to see some documentation. Does anyone have such documentation.

No documentation, but I found a couple of other topics where this is discussed.

Wow! This is the oldest DB that I have seen. They were still working in the latest version of Pan6. I am pretty sure that the above explanation is correct, but I will test it against the Pan6 version.