Try a hash of arrays. For example,

my (%data);

while (<DATA>) {
    my ($submitter, $ticket_number) = split(/\|/);
    push(@{$data{$submitter}}, $ticket_number);
}

print "Submitters, by ticket count:\n";
foreach my $sub 
  (sort { scalar $#{$data{$a}} <=> $#{$data{$b}} } keys %data) {
    print $sub, ": ", scalar $#{$data{$sub}}, "\n";
}

print "\n", "Submitters and tickets, ordered by submitter:\n";
foreach my $sub (sort keys %data) {
    print $sub, ": ", join(", ", @{$data{$sub}}), "\n";
}

__DATA__
Joe|1
Joe|2
Gary|3
Gary|4
Kelly|5
Joe|6
Joe|7
[download]

The above sample would give you something along the lines of:

Submitters, by ticket count:
Kelly: 1
Gary: 2
Joe: 4

Submitters and tickets, ordered by submitter:
Gary: 3, 4
Kelly: 5
Joe: 1, 2, 6, 7
[download]

See also perldsc, for more information on data structures in perl. Hope that helps.

Update: 23 Mar 2005 - Fixed typo in code sample; added note regarding perldsc.