my @a = (
  [4129290, 1675967, 2412031, '41%', '/usr/bin' ],
  [4129290, 1675967, 2412031, '41%', '/usr'     ],
  [4129290, 1675967, 2412031, '41%', '/local'   ],
);
sorter(@a);

__END__
output
======
before sort: /local
Sorted by drive: /usr/bin

##</code><code>##

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

shift(@df_k); # Remove header.

my @sorted_by_drive =
   sort { $a->[5] cmp $b->[5] }
      map { [ split(/\s+/, $_, 6) ] }
         @df_k;


use Data::Dumper ();
print(Data::Dumper->Dump(
   [    \@sorted_by_drive   ],
   [qw(  $sorted_by_drive  )],
));

##</code><code>##

sub parseIntoArraySolaris (@df)
                            ^^ what does this mean?
                               It compiles, surprisingly,
                               but it's not listed in
                               docs and it doesn't give
                               the args to the var @df.

##</code><code>##

sub parseIntoArraySolaris {
   my @rows;
   my $element;

   foreach $element (@_) {
      my ($a, $b, $c, $d, $e, $f) = split(/\s+/, $element);
      push(@rows, [ $b/1024, $c/1024, $d/1024, $e, $f ]);
   }

   return @rows;
}

##</code><code>##

sub parseIntoArraySolaris {
   return map {
      my ($a, $b, $c, $d, $e, $f) = split(/\s+/, $_);
      [ $b/1024, $c/1024, $d/1024, $e, $f ]
   } @_;
}

##</code><code>##

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

shift(@df_k); # Remove header.

my @beforeSort = parseIntoArraySolaris(@df_k);

my @sorted_by_drive =
   sort { $a->[4] cmp $b->[4] }
      @beforeSort;

use Data::Dumper ();
print(Data::Dumper->Dump(
   [    \@sorted_by_drive   ],
   [qw(  $sorted_by_drive  )],
));

##</code><code>##

# 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  )],
));