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

my $x;
$x = $x+1;

print $x;

##</code><code>##

Use of uninitialized value in addition (+) at tmp.pl line 6.

##</code><code>##

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

my $x;
$x = $x ? $x+1 : 1;

print $x;