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

	enum {
		S0, S1, S2, S3, S4, S5, S6, S7, S8, S9
	} state;

	state = S0;

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

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

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

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

		case S4: /* e.g. "var1" */
			switch ((unsigned char) *p) {
			case ' ': break;
			case '=': state = S5; break;
			default:  return -1; /* leaf */
			}
			break;

		case S5: /* e.g. "var1=" */
			switch ((unsigned char) *p) {
			case ' ': break;
			case 'v': state = S6; break;
			default:  return -1; /* leaf */
			}
			break;

		case S6: /* e.g. "var1=v" */
			switch ((unsigned char) *p) {
			case 'a': state = S7; break;
			default:  return -1; /* leaf */
			}
			break;

		case S7: /* e.g. "var1=va" */
			switch ((unsigned char) *p) {
			case 'r': state = S8; break;
			default:  return -1; /* leaf */
			}
			break;

		case S8: /* e.g. "var1=var" */
			switch ((unsigned char) *p) {
			case '2': state = S9; break;
			default:  return -1; /* leaf */
			}
			break;

		case S9: /* e.g. "var1=var2" */
			switch ((unsigned char) *p) {
			case ' ': break;
			default:  return -1; /* leaf */
			}
			break;

		default:
			; /* unreached */
		}
	}

	/* end states */
	switch (state) {
	case S9: return 0x1; /* " *var1 *= *var2 *" */
	default: return -1; /* unexpected EOT */
	}
}