use Set::Scalar;

my %hash;
while (<DATA>) {
    chomp($_);
    my ($first, $second) = split(/s+/, $_);
    if (!exists $hash{$first}) {
        $hash{$first} = new Set::Scalar();
    }
    $hash{$first}->insert($second);
}

foreach my $key (keys %hash) {
    print "The Key is: $key\n\t",
          join("\n\t", $hash{$key}->members()),
          "\n";
}