Re

mod re: sig {
    /// return true if the string is matched by #pat, otherwise return false.
    /// return an error if #pat is invalid.
    val is_match: fn(#pat:string, string) -> Result<bool, `ReError(string)>;

    /// return an array of instances of #pat in s. return an error if #pat is
    /// invalid.
    val find: fn(#pat:string, string) -> Result<Array<string>, `ReError(string)>;

    /// return an array of captures matched by #pat. The array will have an element for each
    /// capture, regardless of whether it matched or not. If it did not match the corresponding
    /// element will be null. Return an error if #pat is invalid.
    val captures: fn(#pat:string, string) -> Result<Array<Array<Option<string>>>, `ReError(string)>;

    /// return an array of strings split by #pat. return an error if #pat is invalid.
    val split: fn(#pat:string, string) -> Result<Array<string>, `ReError(string)>;

    /// split the string by #pat at most #limit times and return an array of the parts.
    /// return an error if #pat is invalid
    val splitn: fn(#pat:string, #limit:i64, string) -> Result<Array<string>, `ReError(string)>;
}