That path looks like it's for the 19c database, not the instantclient. Depending on how Oracle is installed (often out of our hands, by DBAs etc), you may not have everything you need to build DBD::Oracle, hence why I suggested getting the components listed in the modules README, setting ORACLE_HOME (and LD_LIBRARY_PATH) as required then building the module. From experience this is more likely to be successful, less likely to run into some Oracle related shenanigans.