I would tend to agree with roboticus on this one. If you are getting a coredump when using a SID something is wrong and although you only know about one thing being broken right now it may turn out you've got other problems you have not found yet.
However, I'm a little surprised at the comment "not allowed to (nor willing to) change all the code we have to cope for this stupid bug" as a) I find it difficult to see just how much code you'd have to change for a change in connect calling (how many calls to connect can you have scattered around) b) you have not ascertained where the problem is yet and c) the use of "stupid bug" doesn't seem too productive. We don't know where the problem lies; it may be in your perl, DBD::Oracle, OCI, NET8, the way any of them were built or perhaps it is a fixed problem and you are using old versions. Did it ever work on this machine and did you install DBD::Oracle without running the tests or install it after running the tests and some of them failed.
Step back and check sqlplus out with your SID to check that is working then if that works move on to unpacking DBD::Oracle, building it and running the tests - do they pass? If you still have problems the dbi-users mailing list is a good place to start but make sure you post the relevant information like platforms, perl -V, versions of modules etc.