Fyracle

Fyracle solves that problem by matching such syntax idiosyncrasies and by providing the ability to compile and execute PL/SQL procedures unchanged.
The Fyracle Run-time Kit contains a full Firebird installation and the run-time part of oracle-mode.

The run-time kit does not include the Oracle-mode developer tools and documentation. If you all you want is too run a pre-compiled application, the run-time kit is all you need.

If you want to develop with oracle-mode Firebird, you need the Fyracle Developer Kit. This kit includes a GUI tool to modifiy database objects and a command line PL/SQL compiler, which can also handle DDL scripts.