my $string= ' ' x 2**19;
$string= '';

##</code><code>##

length( $string )= 2**19; # Doesn't work

##</code><code>##

open NUL, "<", File::Spec->devnull();
sysread( NUL, $string, 2**19-length($string), length($string) );
close NUL;

##</code><code>##

sysread( STDOUT, $string, 2**19 );

##</code><code>##

sub grow
{
    sysread( DATA, $_[0], $_[1] );
}
__DATA__