DBD::Sybase doesn't have any such limitation - but the underlying API (freetds, Open Client, etc) could very well have a limit. By default Open Client will limit you to 255 chars unless you are using a recent version (12.5 or later), and for freetds you probably need to be using TDS version 7 or 8 to get more than 255 chars for a char string with a placeholder.

Of course - the way to test this is to write a simple insert with a string of a known length and see what you get on the other end (i.e. in the database table)

Michael