This patch was not fully tested because the actual behavior intended
by constraints 'o' and 'e' was apparently never implemented here.
But it had no chance of success as with:
my $sth = $dbh->prepare("");
This uses the inteneded query, removes unneeded $sth->finish calls and
fixes *some* redeclaration of my $variables in the same scope, as
would be needed to run under warnings pragma.