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From: PerlFAQ Server on 27 Mar 2010 00:00
This is an excerpt from the latest version perlfaq4.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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4.63: Why don't my tied hashes make the defined/exists distinction?

This depends on the tied hash's implementation of EXISTS(). For example,
there isn't the concept of undef with hashes that are tied to DBM*
files. It also means that exists() and defined() do the same thing with
a DBM* file, and what they end up doing is not what they do with
ordinary hashes.



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are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
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