* | `d` | data | void *, {mrb_data_type} const | 2nd argument will be used to check data type so it won't be modified; when `!` follows, the value may be `nil` |
* | `I` | inline struct | void * | |
* | `&` | block | {mrb_value} | &! raises exception if no block given. |
* | `*` | rest arguments | {mrb_value} *, {mrb_int} | Receive the rest of arguments as an array; `*!` avoid copy of the stack. |
* | `*` | rest arguments | const {mrb_value} *, {mrb_int} | Receive the rest of arguments as an array; `*!` avoid copy of the stack. |
* | <code>\|</code> | optional | | After this spec following specs would be optional. |
* | `?` | optional given | {mrb_bool} | `TRUE` if preceding argument is given. Used to check optional argument is given. |