Are you looking for something similar to :

use strict;
use Data::Dumper;

my %hash;
while (<DATA>) {
    chomp;
    my ($key, $value) = split /\|/, $_;
    my @values = split /,/, $value;
    if (defined $hash{$key}) {
        push @{$hash{$key}}, \@values;
    }
    else {
        $hash{$key} = [\@values];
    }
}

print Dumper \%hash;

__DATA__
9344220001|sei10720013,21/07/2009-00-00-00,23/07/2009-12-34-44
9344220001|sei10720014,23/07/2009-20-00-23
9344220002|sei10720015,21/07/2009-00-00-00,23/07/2009-12-34-44
9344220003|sei10720016,23/07/2009-20-00-23
9344220003|sei10720017,23/07/2009-20-00-23
9344220003|sei10720018,23/07/2009-20-00-23
[download]

Output is as followed:

$VAR1 = {
          '9344220003' => [
                            [
                              'sei10720016',
                              '23/07/2009-20-00-23'
                            ],
                            [
                              'sei10720017',
                              '23/07/2009-20-00-23'
                            ],
                            [
                              'sei10720018',
                              '23/07/2009-20-00-23'
                            ]
                          ],
          '9344220002' => [
                            [
                              'sei10720015',
                              '21/07/2009-00-00-00',
                              '23/07/2009-12-34-44'
                            ]
                          ],
          '9344220001' => [
                            [
                              'sei10720013',
                              '21/07/2009-00-00-00',
                              '23/07/2009-12-34-44'
                            ],
                            [
                              'sei10720014',
                              '23/07/2009-20-00-23'
                            ]
                          ]
        };
[download]

I hope this helps.