[tmp]$ cat broomduster.pl
open my $fh, '>', 'zeros'  or die "error opening fh: ($!)";
binmode $fh;
print $fh pack "x".(1024*1024*10);

[tmp]$ rm zeros; perl broomduster.pl; ls -lh zeros; du -h zeros
-rw-rw-r-- 1 duelafn 10M 2008-10-09 22:17 zeros
11M     zeros

##</code><code>##

[tmp]$ cat duelafn.pl
open my $fh, '>', 'zeros'  or die "error opening fh: ($!)";
seek $fh, 1024*1024*10 - 1, 0;
print $fh "\0";

[tmp]$ rm zeros; perl duelafn.pl; ls -lh zeros; du -h zeros
-rw-rw-r-- 1 duelafn 10M 2008-10-09 22:17 zeros
12K     zeros