The original poster is saying that the Perl code is his application. He's using the Oracle Instant Client as the source for the libraries needed by DBD::Oracle.

The answer to the problem is that you have to set then LD_LIBRARY_PATH before invoking the Perl script. You can do this by using a shell script to call your Perl script, by setting environment variables manually, or, if the Perl script is a CGI script invoked by Apache, using the SetEnv directive in the httpd.conf.