Sorry for late answer. General syntax for quoting identifiers in SQL is the double quote ("), so your statement should look like:

$sql = q(select * from sms where "System Status" = 'foo');

If you want use placeholders, ensure that they are not quoted:

$sql = q(select * from sms where "System Status" = ?);

Best source for help on DBD::AnyData, DBD::CSV and DBD::DBM would be the dbi-users@perl.org mailing list.