Compare the database data bytewise (old versus new). Log each function's input arguments, compare the logs on the old and new systems. Run each function on the old and new system, compare the returned data (should have been covered by tests).
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]