As I've said before, using perl as a shell script language is not really the best use of perl, nor your CPU. Especially when the pure-perl solutions can be just as fast (or faster) and easier to get right.

Check out cog's module, Filesys::DiskUsage. It can do this much more simply, and much more perlishly.

use Filesys::DiskUsage qw/du/;

my $fullpath = '/tmp/dir*';
my $sum = du({'sector-size' => 4096, 'symlink-size' => 4096}, glob $fu
+llpath);
[download]

I'm using a size of 4096 above as that seems to be a normal size nowadays for some reason. If you want the individual entries' sizes, you can also pass in 'make-hash' => 1 as an option in the hashref of options. Then the answers should come back in a hash where the key is the file/directory, and the value is the size.