use strict; use warnings;
my %hash;
while (<DATA>) {
    s/\s+$//;
    my ($key1, $key2) = split /\s+/, $_;
    $hash{$key1}{$key2}++;
}
for my $k1 (sort keys %hash) {
    print "$k1: ", join(", ", sort keys %{$hash{$k1}}), "\n";
}
__DATA__
Lemon Juice
Lemon Cake
Apple Cider
Lemon Cake
Apple Butter
Apple Sauce
Apple Juice
Lemon Juice

##</code><code>##

Apple: Butter, Cider, Juice, Sauce
Lemon: Cake, Juice