This looks like a bug in your DBD::Oracle but in any case you shouldn't be using RaiseError if you plan on testing the return codes.

Setting RaiseError as you do will cause an exception to be thrown on all errors (except I think errors during the connect() call). That means that $dbh->prepare should either throw an exception or return a valid statement handle.

Also, testing with mysql throws an error only when you execute the query object. Oracle might behave differently ofcourse:

use strict;
use warnings;
use DBI;
my $dbh = DBI->connect( "dbi:mysql:test", "root", "", {AutoCommit => 0
+, RaiseError => 1, PrintError => 0}) || die "Can't connect to databas
+e: $DBI::errstr";

my $qry = $dbh->prepare(q{ select BAD__column from users where id=1254
+3256 }) or die "Prepare bad: $DBI::errstr";

$qry->execute();
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output:

DBD::mysql::st execute failed: Table 'test.users' doesn't exist at tes
+t.pl line 8.
Issuing rollback() for database handle being DESTROY'd without explici
+t disconnect().
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