Except as otherwise provided in this chapter, every attorney for the Commonwealth, special counsel, sworn investigator, and member of a regular, special, or multi-jurisdiction grand jury shall keep secret all proceedings which occurred during sessions of the grand jury; provided, however, in a prosecution for perjury of a witness examined before a regular grand jury, a regular grand juror may be required by the court to testify as to the testimony given by such witness before the regular grand jury.