begin
  string(255)s
  s = "left" . "right"
  printstring(s); newline
  s = "left" . "middle" . "right"
  printstring(s); newline
  s <- "left" . "right"
  printstring(s); newline
  s <- "left" . "middle" . "right"
  printstring(s); newline
endofprogram