#!/usr/bin/perl
use warnings;
use strict;

my @data = (100, 10, 0, undef, q());

no warnings qw( uninitialized numeric );
for my $token (@data) {
    printf "PLAIN |%d|\tDEFINED ", $token;
    printf defined $token ? "|%d|\t" : "\t", $token;
    print "LENGTH ";
    printf length $token ? "|%d|\n" : "\n", $token;
}