use warnings;
BEGIN { $^W = 0; }
my $s = '' . undef();  # Use of uninitialized value

##</code><code>##

no warnings;
BEGIN { $^W = 1; }
my $s = '' . undef();  # [No warnings]

##</code><code>##

use strict;
use warnings;

sub test (&) {
    my $code = shift;
    local $^W = 0;
    $code->( undef );
}

test {
    print "@_";   # Use of uninitialized value
};