undef $/;
my @args = split /\n/, <DATA>;
for(my $idx=4;$idx<@args+4;$idx+=5){
    print join(" ", @args[$idx-4..$idx]), "\n";
}

__DATA__
host1
host2
host3
host4
host5
host6
host7
host8
host9
host10
host11
host12
[download]

There's probably a better way, but i can't think well at this late hour.