I would attack this with a hash to filter out duplicates:

while(<FH>){
 chomp;
 my @fields = split;
 my $ip = shift @fields;
 foreach ( @fields ){
  $masterhash{$ip}{$_} = 1;
 }
}
[download]

Now the hash will contain an unique IP as key with a hash as value of which the keys are uniqe aliases..
So now just print it out:

for my $ip ( keys %masterhash ){
 print "$ip ", join (" ",keys %{$masterhash{$ip}}),"\n";
}
[download]

Hope this helps... (not tested)