Perl is asking you to look hard at line 19...

You must run the 'do' on a defined database handle. The database handle is ruturned by the DBI->connect method. In your code this handle is stored in $db_object (I think $dbh would be a better identifier - database Handle).

Change line 19 to: $db_object->do($sql);

I think you want to use the prepare/execute methods when working with SQL Selects as the do method does not return a statement handle (see perldoc DBI for more info)