Lefty was an early interpreter for graphics programming. It’s from about 1990 or 91, and we used it as the basis for a scriptable graphviz viewer, dotty. It was student code written by Lefteris Koutsofios. I thought there was some C code for parsing graphs but I could be wrong.
Even libast came into the picture much later, but I suppose that was done to clean up some of its OS dependencies or to make it more portable or robust in some way.
I’m ok with retiring it.