#! /usr/bin/perl 

use strict ;
use warnings ;

local $\ = "\n" ; # some formatting
my %h ;
print ( defined %h ? "Defined!" : "Undefined!" );

undef( %h ) ;
print ( defined %h ? "Defined!" : "Undefined!" );

%h = undef ;
print ( defined %h ? "Defined!" : "Undefined!" );

undef( %h ) ;
print ( defined %h ? "Defined!" : "Undefined!" );

#OUTPUT
#Undefined!
#Undefined!
#Defined!
#Undefined!