I don't know fsutil, but I think grep is right: you should use File::Find.

However, some more remarks:

• eq compares strings, != compares numbers.
• grep is only for lists; use eq or $str =~ /foo/ to match strings.
• It's always helpful to to check the return values of open and (especially when dealing with command pipes) close
for errors.
• Rather than embedding variables in commands, I prefer to use the several-argument form of open:
  open my $handle, '-|', 'fsutil', 'fsinfo', 'drivetype', $letter or die $!;

Hmm, it seems kind of funny that I have two links with the same title. In case you did not notice, one is for the user and one is for the function ;-)