sub a_query_builder{
my ($table_name, $display_cols_ref, $where_cols_ref) = @_;

if ($where_cols_ref->{'year_min'})     { push @clauses, "Year >= $where_cols_ref->{'year_min'}" }
if ($where_cols_ref->{'year_max'})     { push @clauses, "Year <= $where_cols_ref->{'year_max'}" }

# ...
$clause = join(" AND ", @clauses);
$display_cols = join(",", @$display_cols_ref);
$sth = $dbh->prepare("SELECT $display_cols FROM $table_name WHERE $clause");
}