To use split, you can reverse the string with the names, only split enough times (6) so that the last string contains the '.', reverse the order of the elements in the foreach loop, then (un)reverse the string when you print it.

my @names = split(/\./, reverse("Pugh.Pugh.Barney.McGrew.Cuthbert.Dibb
+le.Grub"), 6);
foreach(reverse(@names)) {print reverse . "\n";}

__RESULT__
Pugh.Pugh
Barney
McGrew
Cuthbert
Dibble
Grub
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