Prosecutors are contemplating charges against a former state prison bookkeeper who state auditors allege siphoned off more than $100,000 from inmates` personal funds. Details were disclosed today in a report to the Legislative Joint Auditing Committee. According to the audit, a former bookkeeper at the Benton Unit wrote 172 inappropriate checks totaling $92,145 from the Inmate Personal Funds Account. Another $8,085 in cash withdrawals for work release inmates was unaccounted for. The employee has been fired. None of the money has been recovered.