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Perhaps the way to go would be making the three modules into just one: Tie::Hash. Same with Tie::Array and Tie::Scalar.
Looking again at the source, there is a pattern in Tie::Array, Tie::Hash, and Tie::Handle, hidden between the nonsense code: All three classes implement methods for inheriting classes that do NOT depend on the actual implementation of the class, but use existing primitive methods. And I think that for this reason, we should keep the class names and functionality as they are now. The generic class implements generic methods that allow omitting some methods in inheriting classes, even with completely different inner structures, and the Std* class implements standard behaviour based on a trivial blessed reference of the respective type.
In case of Tie::Hash, there is only CLEAR() that slowly clears the tied hash by iterating over all keys and removing them one after the other. Consequentially, both Tie::StdHash and Tie::ExtraHash implement faster variants that simply assign an empty list to the internal hash.
All of the other methods in Tie::Hash are just code that complains where perl would also complain without any extra code. use Carp, use warnings::register, and the methods new(), TIEHASH(), and EXISTS() can simply be removed from Tie::Hash.
The methods UNSHIFT, SHIFT, CLEAR, PUSH, POP, and SPLICE, and EXTEND in Tie::Array are again generic methods that do not depend on the implementation.
The remaining methods EXISTS and DELETE in Tie::Array just complain, and DESTROY is redundant. They all should be removed.
Tie::StdArray implements standard array behaviour in short and efficient code, reimplementing most of the methods in Tie::Array with faster code.
A scalar is so simple that it needs only three methods. All of them are primitive and can not be replaced by calls to other methods. Consequentially, Tie::Scalar contains only code to complain, all of it should be removed: All methods, use Carp, and use warnings::register. What remains is POD, the package Tie::Scalar, and our $VERSION. Moving Tie::StdScalar to Tie/StdScalar.pm breaks backwards compatibility, so use Tie::StdScalar should be added to Tie::Scalar. Also, Tie::StdScalar should keep inheriting from the empty Tie::Scalar.
Yes, it looks like nonsense. But it allows to add more methods to a tied scalar class in future perl versions, and having a sane default for the extra methods in either Tie::Scalar or Tie::StdScalar.
Tie::Handle once again contains some generic methods (PRINT and PRINTF use WRITE, GETC uses READ), and several complaining methods (TIEHANDLE, READLINE, READ, WRITE, CLOSE), as well as the useless new(). new() and the complaining ones have to go. Tie::StdHandle implements all standard methods, and a simpler version of GETC. No changes needed here, except for the wrong class name in the SYNOPSIS section of the POD.
Backwards compatibility needed?
I wanted to know which CPAN modules use one of the Tie::* classes, and which of those modules actually use the new() nonsense. https://grep.metacpan.org/search?size=20&q=Tie%3A%3A&qd=*&qft= runs into an HTTP 500 error. Is there a better way than downloading and unpacking the entire CPAN?
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)