As mentioned earlier in this thread, Perl uses "" for false. It does not use undef. 
$i = undef;  print(defined($i) ? "[$i]" : 'undef', "\n");
$i = !1;     print(defined($i) ? "[$i]" : 'undef', "\n");

__END__
output
------
undef
[]

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In reply to Re^2: Logical expression evaluation by ikegami
in thread Logical expression evaluation by nghosh

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