Sorting IP addresses 

• Schwartzian Transform

my @sorted =
    map { $_->[0] }
    sort {
        $a->[1] <=> $b->[1] or
        $a->[2] <=> $b->[2] or
        $a->[3] <=> $b->[3] or
        $a->[4] <=> $b->[4]
    }
    map { [ $_, split /[.]/ ] } @addr;