To get the values of a single column for all rows matching a query do:

my $aryref = $dbh->selectcol_arrayref( $sql,{},@binds );

To get the value of a single column for a single row matching a query do:

my($value) = $dbh->selectrow_array( $sql,{},@binds );

In both cases, the SQL query should specifiy only a single column in the SELEC list, e.g. SELECT foo FROM ...