You'll really need to give a bit more code but a few things to look at are:

If you don't want DBI to die then make sure that the RaiseError attribute is off.

Checking the errstr method is the right way to go for getting the error but you must check it as soon as you can since most DBI method calls will reset it to undef.

You mention that you can't use eval blocks due to your app framework. have you considered using a local die handler to override the behaviour and then use an eval block?

{
 local $SIG{__DIE__}  = sub {# feedback code here};
 eval {
 # your DBI code
 };
}
[download]

Outside of the block your framework's handler will be in effect.

DBI also provides a HandleError attribute which sets an error handler specifically for errors from DBI. Check the docs for more info on this DBI