type t = | String | Any atom. |
| Bool | One of true, false, True, or False. |
| Char | A single-character atom. |
| Float | An atom which parses as a float. |
| Int | An atom which parses as an integer, such as int or int64. |
| This of {ignore_capitalization : bool; | string : string; |
} | Exactly that string, possibly modulo case in the first character. |