#!/usr/bin/perl -w

my $a = 1;
my $b = 2;
my $c = 3;
my $d = 4;
my $e;

print "$a $b $c $d $e\n";

##</code><code>##

Use of uninitialized value in concatenation (.) or string at C:\testperl\undef.pl line 9.
1 2 3 4