Peter Weinberger in an interiview mentioned a language called Poplar
What’s interesting is that at the same time that we were doing AWK, there was a project at Xerox PARC called Poplar … maybe called Poplar. Anyway, whatever it was called, there was this project at Xerox PARC, which had fairly similar goals. That is they were going to take these files consisting of a lot of characters and you break them apart in various ways and you process them using some language and you pass them on. And they put a lot of work into clever ideas. It was a functional programming language. ... And it was supposed to be user friendly and in addition you wrote the program sort of here and then you worked an example on the other side of the page and the compiler checked that the program worked the example the same way you had. So that you had some feeling for what the program was doing
Is there more information about this language? Or it's just the Parc's internal project that never left their laboratories?