use strict;
use warnings;
my $x="";
foo( substr($x,2,1) ); # crashes here
print "Alive!\n"; # not reached
sub foo {}

##</code><code>##

use strict;
use warnings;
my $x="";
my $y=substr($x,2,1); # warns, doesn't crash
foo($y); # no-op
print "Alive\n"; # we get here just fine
sub foo {}