=====================================
regular character
=====================================

?a
?Z
?0
?9
?_
??

---

(source
  (char)
  (char)
  (char)
  (char)
  (char)
  (char))

=====================================
escaped character
=====================================

?\n
?\t
?\s
?\\
?\a
?\b

---

(source
  (char)
  (char)
  (char)
  (char)
  (char)
  (char))

=====================================
list of char literals
=====================================

[?a, ?b, ?c]

---

(source
  (list
    (char)
    (char)
    (char)))