Yes, it's the version of SQL::Statement. I recently fixed the empty string parsing. In general it's better to use placeholders or to use NULL instead of empty string, but your problem should be fixed in the most recent SQL::Statement. I'm debugging some errors in the make test for the latest statement but you can safely ignore the test failure and install it anyway, it's a test problem, not a module problem.

update please let me know if this fixes your problem.