sub arrayref_to_csvline { ... }

my $headers;
while (my $row = $iter->())
{
  unless ($headers)
  {
    print arrayref_to_csvline($row->fields);
    $headers = 1;
  }
  print arrayref_to_csvline($row->values);
}

##</code><code>##

sub arrayref_to_csvline { ... }

my $headers;
while (my $row = $iter->())
{
  $headers ||= print arrayref_to_csvline($row->fields);
  print arrayref_to_csvline($row->values);
}