It can't ever work, because of the problem of references.

Storable supports circular references correctly, and the implementation of this means that what is in $_[0] may already have 4 or 5 other Perl references pointing to it by the time the hook gets called.

So if you were to replace $_[0] with $singleton, you would break all the other references.

If Perl references were purely heirachal, this wouldn't be a problem.

And that is why we have a seperate method. Because it provides an alternative that certifies that that class won't end up creating circular references below it, and thus that a modify/return type result will work sanely.

Read through bug #4901 and you might be able to understand it a bit more. It took me a long time.

In reply to Re^4: Safely altering the behaviour of heavily used modules by adamk
in thread Safely altering the behaviour of heavily used modules by adamk

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