use strict;
use warnings;

my $tainted = shift;
my $test;

$test = undef;
$test += $tainted;
print "Test 1: $test\n";

$test = undef;
$test += $tainted;
print "Test 2: $test\n";

##</code><code>##

perl -T test.pl 1

##</code><code>##

%perl -T test.pl 1
Test 1: 1
Use of uninitialized value in addition (+) at test.pl line 12.
Test 2: 1