my @level;

&myfunc($number, $company, \@level, 0, $dbh);

print $#level;   # prints -1

sub myfunc {
    my ($manager_no, $company_id, $level_ref, $index, $dbh) = @_;
    my ($employee_no, $emp_company_id);
    my ($sql, $sth);   
    my @level = @$level_ref;
    
    $sql = 'query';
    $sth = $dbh->prepare($sql);
    if ( !($sth->execute($manager_no, $company_id)) ) {
	die;
    }
    while ( ($employee_no, $emp_company_id) = $sth->fetchrow_array() ) {
	if ( exists $level[$index]{"$employee_no-$emp_company_id"} ) {
	    $level[$index]{"$employee_no-$emp_company_id"} = 1;
    }
	else {
	    if ( ( $employee_no eq $manager_no) && ($emp_company_id eq $company_id) ) {
		# do nothing
	    }
	    else {
		$level[$index]{"$employee_no-$emp_company_id"} = "$manager_no-$company_id";
		&myfunc($employee_no, $emp_company_id, $level_ref, $index + 1, $dbh);
	    }
	}
    }
}