summarise-hostnames

summarise-hostnames.pl

sub summarise_hostnames {
    my @hostnames = @_;
    for my $entry (@hostnames) {
        say "Consider $entry";
        my ($leaf, $domain) = split /\./, $entry, 2;
        if ($domain =~ /\./) {
            say "OK, add $leaf to $domain list";
            push @{ $leaf_by_domain{$domain} }, $leaf;
        } else {
            say "Treat $entry as a domain only";
            push @domains, $entry;
        }
    }
    return join ', ', 
        (
        map {
            @{$leaf_by_domain{$_}} == 1
                ? $leaf_by_domain{$_}[0].'.'.$_
                : "{" . 
                    join(',', sort @{ $leaf_by_domain{$_} }) .
                    "}." . $_
        } sort keys %leaf_by_domain
        ),
        @domains;
}