perlsyn:

Truth and Falsehood

The number 0, the strings '0' and "" , the empty list (), and undef are all false in a boolean context. All other values are true. Negation of a true value by ! or not returns a special false value. When evaluated as a string it is treated as "", but as a number, it is treated as 0. Most Perl operators that return true or false behave this way.

I'm assuming this is the missing piece of documentation that explains why defined always returns a defined value.

In reply to Re: defined defined -- Bug or "Feature"? by Anonymous Monk
in thread defined defined -- Bug or "Feature"? by roho

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