Hi, I googled "DBI bind LOB max length" and came up with this link: Handling LONG/LOB Data.
This and related links appear to answer your question. However, I am not completely sure that this link isn't a copywrite infringement. If it is then I or the janitors will remove this link.
Update: I removed the link - it now goes nowhere.
Comment on Re: How to set 'max_len' for DBI 'bind_param'