Thanks for your reply, Tommy!

I tried "$dbh->{ShowErrorStatement} =1" as well as "$inssth->{ShowErrorStaement = 1" without any visible change in the error message.

The statement handles are indeed varying so I cannot use "$sth->Statement".

Some improvement though gives:

$dbh->{HandleError} = sub {
  warn $DBI::lasth->{Statement};
  Carp::confess;
}
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Now the error messages looks like:

insert into mytable values ( ?, ? )
main::__ANON__('DBD::Oracle::st execute failed: ORA-01722:
...
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I found a message from Tim Bunce in perl.dbi.dev that he is planning an extension for showing the bound parameters as well. That means for the moment I'm stuck unless I give up the placeholders.