perl undef

Undefined values can be set using the undef function. Alternatively, the value of the variable specified in the argument is undefined.

#!/usr/bin/perl --

use strict;
use warnings;

print "Content-type:text/html\n\n";
my $name = "Kimoto";
$name = undef;

if (defined $name){
	print "defined";
} else {
	print "Undef";
}

なるほどー