sub compare_num1_LT_num2 {
  my ($first, $second) = @_;
  return ($first <= $second);
}

sub validate {
  my $data_in = shift;
  my $maxint = 10000;

  my $profile = {
    'required' => [ qw( Field1 Field2 ) ],
    'msgs' => { 'prefix' => 'err_' },
    'constraints' => {
      'Field1' => sub { 
        my $in = shift; 
        $in =~ /^\d+$/ && $in > 0 && $in < $maxint
      },
      'Field2' => sub { 
        my $in = shift; 
        $in =~ /^\d+$/ && $in > 0 && $in < $maxint },
      'Field2_LT_Field1' => {
        'constraint' => 'compare_num1_LT_num2',
        'params'     => [ qw/ Field1 Field2 / ],
      },
    },
  };

  my $results = 
   Data::FormValidator->check($data_in, $profile);
}  

validate(\%data);