My background was 9 years of Fortran, then 25 years of nothing, then 10
years of FutureBasic.

Perhaps I misunderstood how parameters worked in a function call. I have had
the impression that variables/arrays included in a function call could be
accessed ("read") by the function, but not successfully modified within the
function ("written"). This was a distinct difference from my Fortran
experience where the addresses were passed and any actions within the
subroutine affected the variables/arrays passed to it.

It was this perhaps misunderstanding that caused me to use globals for any
routines that needed to change multiple variables/arrays beyond the single
variable that could be passed back as result=fn whatever(variable1, array2,
etc).

My apologies for my ignorance.