foo (1, 2, 3). ; (1) Ordinary call
foo ().        ; (2) No arguments
foo.           ; (3) Equivalent to (2)
foo (1).       ; (4) Single-argument function
foo 1.         ; (5) Equivalent to (4)
foo (bar).     ; (6) Parentheses necessary here since bar is not a literal
foo: 1, 2, 3.  ; (7) Alternative syntax, equivalent to (1)