# Get data.
my @df_k = split(/\n/, `df -k`);

# Remove header.
shift(@df_k);

# Parse line.
foreach (@df_k) {
   my ($a, $b, $c, $d, $e, $f) = split(/\s+/, $_);
   $_ = [ $b/1024, $c/1024, $d/1024, $e, $f ];
}

# Sort.
my @sorted_by_drive = sort { $a->[4] cmp $b->[4] } @df_k;

# Quick way of printing for now.
use Data::Dumper ();
print(Data::Dumper->Dump(
   [    \@sorted_by_drive   ],
   [qw(  $sorted_by_drive  )],
));