I think as long as an $obj->{attribute} is documented as part of the API it's fine to use it. Who am I to worry about the maintenance of a foreign module like DBI.

from DBI docs:

$h->{AttributeName} = ...;    # set/write
... = $h->{AttributeName};    # get/read
[download]

But I'm open to hear from other CPAN modules besides DBI which "decapsulate" their internals.

I have colleagues who thought doing this with undocumented attributes which were only set in the constructor is fine. I disagree strongly.

That's like monkey patching a module or changing parts of a laptop, one shouldn't be surprised about loss of warranty.

> But all approaches that add another layer of indirection between the intention to set a value and the hash access make things slower.

Noteworthy that DBI is adding such a layer:

Attempting to set or get the value of an unknown attribute generates a warning

This will hardly be fast.