That information may not be available. Oracle's OCI supports parameterized queries. The prepare step sends the statement with placeholders to the server for parsing and generation of an execution plan. The data is plugged in on the server at the time of execution. The full statement with data plugged into placeholders is never available to DBI or DBD::Oracle.
There may be other ways to find out, though. I know PostgreSQL can be told to keep a log of the statements it executes. If we knew what database you were working with, maybe someone who knows that database could tell you how to trace at the database.