while (<DATA>) {
    my @pieces = split /\s+/;
    my $id = $pieces[0];
    my $seq = $pieces[-1];
    $results{$id} = [] unless exists $results{$id};
    push @{$results{$id}}, $seq;
}
[download]

Actually, as perlreftut instructs, the line:

 $results{$id} = [] unless exists $results{$id};
[download]

is unnecessary. I highly recommend that you read perlreftut:

$ man perlreftut