int
fsm_main(const char *s)
{
	const char *p;

	enum {
		S0, S1, S2, S3, S4, S5, S6
	} state;

	state = S0;

	for (p = s; *p != '\0'; p++) {
		switch (state) {
		case S0: /* start */
			switch ((unsigned char) *p) {
			case 'c': state = S1; break;
			default:  return -1; /* leaf */
			}
			break;

		case S1: /* e.g. "c" */
			switch ((unsigned char) *p) {
			case 'o': state = S2; break;
			default:  return -1; /* leaf */
			}
			break;

		case S2: /* e.g. "co" */
			switch ((unsigned char) *p) {
			case 'l': state = S3; break;
			default:  return -1; /* leaf */
			}
			break;

		case S3: /* e.g. "col" */
			switch ((unsigned char) *p) {
			case 'o': state = S4; break;
			default:  return -1; /* leaf */
			}
			break;

		case S4: /* e.g. "colo" */
			switch ((unsigned char) *p) {
			case 'u': state = S5; break;
			case 'r': state = S6; break;
			default:  return -1; /* leaf */
			}
			break;

		case S5: /* e.g. "colou" */
			switch ((unsigned char) *p) {
			case 'r': state = S6; break;
			default:  return -1; /* leaf */
			}
			break;

		case S6: /* e.g. "color" */
			return -1; /* leaf */

		default:
			; /* unreached */
		}
	}

	/* end states */
	switch (state) {
	case S6: return 0x1; /* "colou?r" */
	default: return -1; /* unexpected EOT */
	}
}