use English; use strict; 
my $key; my $value;
print "HASH WITH DUPLICATES...\n";
my %mapdup =
(
    1  => "one", 2  => "two",  5  => "five",    # English
    1  => "un",  2  => "deux", 5  => "cinq",    # French
    1  => "ein", 2  => "zwei", 5  => "funf",    # German
    1  => "bir", 2  => "iki",  5  => "bes",     # Turkish
    1  => "yi",  2  => "er",   5  => "wu",      # Mandarin 
);
while (($key, $value) = each %mapdup)
{
    print "($key, $value)\n"  if defined $value;
    print "($key, <undef>)\n" if not defined $value;
}