I believe you have to treat it as a PL/SQL block, and say something more like:

my $sql        = 'BEGIN exec RBC_test( :? ); END;';
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Strictly speaking, calling stored procedures is not supported by the DBI, though some drivers support it. Take a look at the DBD::Oracle documentation for more info.

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DamnDirtyApe

Those who know that they are profound strive for clarity. Those who
would like to seem profound to the crowd strive for obscurity.
            --Friedrich Nietzsche