defined $var ... will return undef (which is a FALSE value) if the variable is undefined.

Sorry, that's not quite correct, compare the outputs of the following:

$ perl -wMstrict -MDevel::Peek -le 'my $x = undef; Dump( $x )'
$ perl -wMstrict -MDevel::Peek -le 'my $x = !1; Dump( $x )'
$ perl -wMstrict -MDevel::Peek -le 'my $x = defined(undef); Dump( $x )
+'

[download]

(Update: Whoops, just saw your update, you saw that yourself)

The rest of your post is excellent though, so no worries about the duplicated efforts, TIMTOWTDI :-) I especially like the comparison with C, and it makes another important point: comparing a true/false value explicitly is brittle: If defined decided to return 0 as a false value instead, then defined(...) eq "" will break!

In reply to Re^4: Regex result being defined when it shouldn't be(?) by haukex
in thread Regex result being defined when it shouldn't be(?) by chenhonkhonk

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