You might want to check your version of DBI...some things have only been added relatively recently. Looking through the changes file for DBI might help.

Also, selectcol_arrayref combines preparing and executing, so it is used against the database handle instead of the statement handle. For example:

$dbh->selectcol_arrayref($statement);

instead of 

$sth->selectcol_arrayref($statement);
[download]

EEjack