The following code will do what you want:

#!/usr/bin/perl
use Data::Dumper;
my %HoA = ();
my %hash_track = ();
while(<DATA>) {
    chomp($_);
    my (@stuff) = split(" ", $_);
    &fill(@stuff);
}

print Dumper(\%HoA);
sub fill() {
    my @a = @_;
    my @ar = @a[0,1,2,4,5,6,7];
    my $h = $a[3];
    $HoA{$h}[$hash_track{$h}] = [ @ar ];     
    $hash_track{$h}++; 
}

__DATA__
334 Capped 28 5034366 16777215 NULL NULL NULL 
373 Capped 28 5034366 16777215 NULL NULL NULL
[download]

output:

$VAR1 = {
          '5034366' => [
                         [
                           '334',
                           'Capped',
                           '28',
                           '16777215',
                           'NULL',
                           'NULL',
                           'NULL'
                         ],
                         [
                           '373',
                           'Capped',
                           '28',
                           '16777215',
                           'NULL',
                           'NULL',
                           'NULL'
                         ]
                       ]
        };
[download]

%hash_track is used to increment the first level %HoA array.

hope this helps,

davidj