Thanks for your reply. I am reading a CSV file(below) and creating a temporary complex hash structure as described to perform some operations. As you can see my $key is the time which should be only one per second and plug the data as hash/array.

NAME,06/01/2011,09:30:00,16.76,756,Q,00
NAME,06/01/2011,09:30:00,16.76,300,Q,00
NAME,06/01/2011,09:30:00,16.76,100,Q,00
NAME,06/01/2011,09:30:01,16.76,100,Q,00
NAME,06/01/2011,09:30:01,16.76,200,Z,00
NAME,06/01/2011,09:30:02,16.77,200,X,00
NAME,06/01/2011,09:30:02,16.77,200,X,00
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Open 100k line CSV file and read using Text_CSV. I have to undef the hashes before jumping to next second.

    my $csv = Text::CSV_XS->new();
    open (FILE, "<", "$tickdir/$file") or die "Can't open CSV File:$! 
+\n";

    while (<FILE>) {
        $csv->parse($_);
        my @columns = $csv->fields();
        my $key = str2time($columns[1].' '.$columns[2]);
        my (@prices, @volumes) = ();
        my %HOH = ();

        $HOH{$key}{"name"} = $columns[0];
        push(@{$HOH{$key}{"price"}}, $columns[3]);
        push(@{$HOH{$key}{"volumes"}}, $columns[4]);

        print Dumper(\%HOH);
    }
    close FILE;
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OUTPUT: As you can see the key values are same.

$VAR1 = {
          '1306935005' => {
                            'volumes' => [
                                           '200'
                                         ],
                            'name' => 'NAME',
                            'price' => [
                                         '16.76'
                                       ]
                          }
        };
$VAR1 = {
          '1306935005' => {
                            'volumes' => [
                                           '400'
                                         ],
                            'name' => 'NAME',
                            'price' => [
                                         '16.76'
                                       ]
                          }
        };
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