open (PRV, "<$private") or die "Cannot read $private: $!";
my %connected;
while (<PRV>) {
    chomp;
    my ($far, $dev) = (split(' ', lc($_)))[0,3];
    push @{$connected{$far}}, $dev;
}

foreach my $dev (sort keys %connected) {
  my $fars = join ", ", @{$connected{$dev}};
  print "$dev is connected to: $fars\n";
}