There is nothing in the code you showed that prints anything. There is only a die. Does the code not die at that point? If not, what code prints the empty string? Do you mean you get an empty string value when you look up a key? Do all lookups produce the same result regardless of key? Was the DBM file generated by the same setup that is failing to read it or did you copy it from elsewhere?

Makeshifts last the longest.