I frequent perl monks a bit and late yesterday an issue came in with DBD::ODBC and Microsoft Access. The perl monks node and rt 46597 detail it all quite well. It appears DBD::ODBC was not following the DBI specification (as it was originally written) to the letter with respect to sticky bound parameter types but since then Tim Bunce has modified the DBI pod slightly to allow DBDs to enable a bound parameter to be rebound with a different type. The change to DBD::ODBC was fairly small but by the time I'd added a test case, bumped the version to 1.21_1 and tested a dozen or so ODBC drivers this consumed a fair amount of time.
Todays unicode problems are with JSON::XS. We are using JSON extensively in the project I am working on and we have a lot of unicode strings. JSON::XS really is the best and fastest perl JSON parser (I've tried them all) and Marc Lehmann who wrote JSON::XS is very knowledgeable and usually quick to respond to any query.