Well, I found the next bug that's holding things up. It has to do with differences between how WProlog and XProlog handle "primitives." Basically, WProlog didn't. XProlog does. WProlog had an interesting hack that allowed some "non-logic" stuff to happen (such as printing), but it has some weird synchronization issues that can be troublesome to keep track of. That's going to go away, but this does mean updating how the parser parses stuff. That might delay the next release beyond this weekend, but I at least have a clear path to follow.