Add todo-test for GH 16665 (surprising precedence issue: sort f()->@*)

[zb226]

This PR adds a todo-test for #16665 where postfix dereferencing fails to work as documented:

Postfix dereference should work in all circumstances where block (circumfix) dereference worked, and should be entirely equivalent.

This snippet using the circumfix syntax prints 123:

sub f {[1,2,3]}; print sort @​{f()}

However, the postfix variant produces no output:

sub f {[1,2,3]}; print sort f()->@*;

With warnings enabled, the postfix variant emits Use of uninitialized value in array dereference.

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There are three related issues linked: #16548, #15733, #2305.
I'm wondering if this is the right issue to todo-test, or the others should even get separate tests.

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• This set of changes does not require a perldelta entry.

[jkeenan]

This PR adds a todo-test for #16665 where postfix dereferencing fails to work as documented.

Can you please cite the place in the Perl documentation that specifies how postfix dereferencing works, and then explain the discrepancy between what you got and what you expected? Thanks.