No person shall be excused from attending and testifying or from producing documentary evidence before the director, the commission, or an appeals examiner, or in obedience to the subpoena of any of them, on the ground that the testimony or documentary evidence required of him may tend to incriminate him or subject him to a penalty or forfeiture; but no individual shall be prosecuted or subjected to any penalty or forfeiture on account of any transaction, matter, or thing concerning which he is compelled, after having claimed his privilege against self-incrimination, to testify or produce documentary evidence except that the individual so testifying shall not be exempt from prosecution and punishment for perjury committed in so testifying.