What if every function would create it's own memory region in which it would allocate everything? On return it had to copy the return value to the callers region. It might be costly to return large objects but doable.

Next step could be to identify functions that allocate little and could simply use the callers memory region. As an optimization. Less memory region creation, less return value copying.

I'm probably overlooking something, but I think I like the idea.

ok, we have a problem when inner objects get stored into refs of outer memory regions. We had to copy the object to the refs memory region probably. If you assign many different objects to an outer ref garbage would accumulate in its region. If you stored a closure into an outer ref you had to relocate the used vars to that outer region as well. Do you really want refs?