Perl 5.8.3 is severely old. The system perl (/usr/bin/perl) is probably newer than that. (5.8.8 IIRC, but I don't have an AIX 5 box anymore to check with.) Do you have to use the perl that is inside Oracle for this? I would suggest installing your own perl and using that. I've been regularly building 5.16.0 and 5.17.* ("blead") on AIX 6 and 7 (7 has a minor issue, but I think IBM has fixed it, just waiting to get the fix applied to the system to be sure). Tux has been building on 5.2 and 5.3 fairly regularly as well. This would resolve your first issue. Failing that, you may be able to "install ExtUtils::MakeMaker" - I'm not sure if that will eventually drag in a newer version of perl and then you're back to installing a private perl again anyway as I wouldn't suggest upgrading the perl included with Oracle.
It also looks like you're mixing 32-bit and 64-bit objects. Or at least 32-bit objects when perl might be compiled for 64-bit (which would make sense since the perl that comes with AIX is 32-bit). Again, a recommendation for a private perl: I've had this issue when compiling against the system perl, but never with a private perl.
I'd also be tempted to ask Oracle if they support you installing additional modules to their private perl. I'd somewhat expect a response like "Um, er... what?" which might also give you impetus to use your own perl. I do expect, however, that there should be no problem connecting to Oracle from your own private perl. You shouldn't require Oracle's perl to connect to their db.