如何使用Ragel正确扫描标识符

identifier = letter (letter | digit)*;

#include<stdio.h>
#include<string.h>

%%{
    machine scanner;

    identifier = letter (letter | digit)*;

    main := |*
        identifier => {
            printf("Found identifier: %.*s\n", fc - ts, ts);
        };
        any => {
            printf("Unknown character: %c\n", *ts);
        };
    *|;
}%%

int main() {
    const char *input = "hello world123";
    const char *p = input;
    const char *pe = input + strlen(input);
    const char *eof = pe;

    %% write data;

    %% write init;
    %% write exec;

    return 0;
}

ragel -C -o scanner.c scanner.rl
gcc -o scanner scanner.c

./scanner

Found identifier: hello
Unknown character:  
Found identifier: world123