PLAnner-like System Modelled on Actors. Carl Hewitt, 1975. The first actor language. Originally called Planner-73, and implemented in MacLisp. Lisp-like syntax, but with several kinds of parentheses and brackets.

["A PLASMA Primer", B. Smith et al, AI Lab Working Paper 92, MIT Oct 1975].

["Viewing Control Structures as Patterns of Passing Messages", C. Hewitt, AI Lab Memo 410, MIT 1976].