foreach my $set ( sort keys %HoHoA)
{
    print "$set\n";
    my @key = keys %{$HoHoA{$set}};

    for ( my $i = 0; $i<@key; $i++ )
    {
        for (my $j=$i+1; $j<@key; $j++  )
        {
           print "$key[$i] - $key[$j]\n";
        }
    }
}
# Am I attacking the problem correctly?