There are several terribly confusing things about the pre-1980 versions of "A Forest". First is that at both the De Melkweg and Le Bataclan shows, they performed it twice. Apparently it is sort of like the reprise of "Seventeen Seconds" during encores on the Picture Tour, although the second versions of this tune are always a minute longer than the first. Another is the actual name of the song; For the first, no name is given, while for the second at De Melkweg, it is called "At Night", and, to make matters worse, has almost the same lyrics as the first version at La Bataclan! I can see the lyrical parallels with the later song, for example the "someone had to watch" line (it makes a lot more sense if you've read Kafka's vignette). Robert was probably working out the kinks with each performance, finally putting a particular set of lyrics to this tune (one of the earliest versions has very similar lyrics to the album version) and putting the "At Night" ones to a more fitting one.