Just so you know, this code:

&{$animal."::speak"};
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doesn't create anything. It uses what's called a "symbolic reference" to look up a subroutine that already exists. A symbolic reference is just a string, and when you try to dereference a string, {}, perl looks up the string in the symbol table, and in this case retrieves the subroutine, &, with that name.

You can use typeglobs to create new entries in the symbol table, for instance:

*Cow::speak = sub {print "mooo\n"};

Cow->speak();

--output:--
mooo
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The rest of your post doesn't make any sense to me.