my $sth_C = $dbh->prepare(
    "select * from result_storage_keep 
     where aggregated_area like ?")
     or die "Couldn't prepare query: " . $dbh->errstr;

foreach my $area (@Geo_areas) {
    next unless $area;

    $sth_C->execute($area) 
        or die "Couldn't execute query: " . $sth_C->errstr;

    while (my @row = $sth_C->fetchrow_array) {
        print OUTPUT_FILE 
            join("\t", map {$_ ? $_ : "''"} @row),
            "\n";
    }       
}   

##</code><code>##

# this only works if this array is small-ish
my $areas = join(", ", @Geo_areas);

# interpolating can be dumb ... 
# unless you trust the data in @Geo_areas...
my $sth_C = $dbh->prepare(
    "select * from result_storage_keep 
     where aggregated_area in ($areas)
     order by aggregated_area")
     or die "Couldn't prepare query: " . $dbh->errstr;

while (my @row = $sth_C->fetchrow_array) {
    print OUTPUT_FILE 
        join("\t", map {$_ ? $_ : "''"} @row),
        "\n";
}