Filesys::Statvfs provides an interface between
Perl and the statvfs() system call.

Filesys::Df uses Filesys::Statvfs to obtain
filesystem statistics then creates additional
filesystem information such as percent full,
user and superuser differentials, etc.

Filesys::Df will also let you specify the
block size for the values you wish to see.
The default block size output is 1024 bytes per
block. So if you want to get the size in bytes
just take the block size and * it by 1024.

WWW: http://search.cpan.org/dist/Filesys-Statvfs_Statfs_Df/