our $lname;
my $sth = $dbh->prepare(<<EOSQL);
  SELECT   sup.fname, sup.lname, sup.title, sup.supervisor,
           emp.fname, emp.lname, emp.title, emp.supervisor
  FROM     employeedb sup
  JOIN     employeedb emp ON .....
  ORDER BY sup.fname, sup.lname, emp.fname, emp.lname
EOSQL
$sth->execute or die $sth->errstr;
my $previous_supervisor = '';
while (my $aref = $sth->fetchrow_arrayref) {
   my ($sup_fname, $sup_lname, $sup_title,
       $emp_fname, $emp_lname, $emp_title) = @$aref;

   # control-break: if a new supervisor is found, skip a few lines and add a header
   my $current_supervisor = "$sup_fname $sup_lname";
   if ($current_supervisor ne $previous_supervisor) {
      $R += 3; $C = 0;
      $worksheet0->write($R, $C++, "SUPERVISOR: ", $format_HEADER);
      $worksheet0->write($R, $C++, $current_supervisor, $format_HEADER);
      $R++; $C=0;
      $worksheet0->write($R, $C++, "First Name", $format_COL_HEADER);
      $worksheet0->write($R, $C++, "Last Name",  $format_COL_HEADER);
      $worksheet0->write($R, $C++, "Title",      $format_COL_HEADER);
      $worksheet0->write($R, $C++, "Supervisor", $format_COL_HEADER);
   }

   # Add employee to sheet
   $R++; $C=0;
   $worksheet0->write($R, $C++, $emp_fname,      $format_NORMAL);
   $worksheet0->write($R, $C++, $emp_lname,      $format_NORMAL);
   $worksheet0->write($R, $C++, $emp_title,      $format_NORMAL);
   $worksheet0->write($R, $C++, $emp_supervisor, $format_NORMAL);
}