For what open(FSUTIL,"fsutil fsinfo drives | "); does, see open.

You don't tell us what "your system" is, but if it is Windows, you'll likely be better off by using one of the native ways to get at the "list of drives", like Win32::DriveInfo, (Win32) Hard Drive Information or DBD::WMI and the appropriate WMI query.

I found all these by searching Google for site:perlmonks.org list of drives.