my %unique;
while ( my $line = <DATA> ) {
    chomp $line;
    my ( $left, $right ) = split /\s+/, $line;
    push @{$unique{$left}}, $right;
}
foreach my $key ( sort keys %unique ) {
    print "$_\t";
    foreach my $item ( @{$unique{$key}} ) {
        print "$item ";
    }
    print "\n";
}