Secondly, the call to bind_columns is a bit off. This is supposed to be an array (see DBI docs)

No, it's supposed to be a list. It could only be an array if bind_columns were prototyped to expect an array. Even if it were, it wouldn't work, as it's a method call, and those ignore prototypes.

Besides all that, your code will be off by one, as a reference to undef doesn't look like undef or a hash reference. I wouldn't be surprised if your code threw "couldn't modify constant item" errors.