EMPTYSTR
    ; Demonstrate how to assign an empty string to a variable.
    set x = ""

      ; Demonstrate how to check that a string is empty.
      ; Length 0 is empty; equality/pattern check are 1=T, 0=F
      write !,"Assigned x to null value.  Tests: "
      write !,"String length: "_$length(x)_", Equals null: "_(x = "")_", Empty pattern: "_(x?."")    ; length 0 is empty

      ; Demonstrate how to check that a string is not empty.  Same as above.
      set x = " "    ;assign to a space - not null
      write !!,"Assigned x to a single blank space.  Tests: "
      write !,"String length: "_$length(x)_", Equals null: "_(x = "")_", Empty pattern: "_(x?."")

      quit