"Can't locate loadable object for module DBI" indicates that DBI (not DBD::Oracle, but DBI itself) is not installed properly, specifically that the XS portion (usually found in auto/* directories) is either not where your perl expects it to be or is not compiled correctly for the platform. If it works on the command line and not in CGI, then make sure both environments are running the same version of perl and if needed, tweak the @INC for the CGI with use lib.