undef is rather like NULL in a database context ... it is "the absence of a value." Any value. Comparison to nothing-at-all has no meaning. But it is valid to test for exists($a) == exists($b), which is True if both are defined or if neither one is.

In reply to Re: why can't compare a variable with undef directly? by Anonymous Monk
in thread why can't compare a variable with undef directly? by Anonymous Monk

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