The return value of CanItemBeReserved is incorrectly used in a condition in CanBookBeRenewed:


                    next unless CanItemBeReserved($borrowernumber,$itemnumber);

CanItemBeReserved returns a hash reference wich always evaluates to true.  The condition should instead be:

                    next unless CanItemBeReserved($borrowernumber,$itemnumber)->{status} eq 'OK';