Something like this maybe?

use strict; use warnings;

my @iostat_system = qx(iostat -x -p -k -d);

my @colnames;
my $ncols=0;
my %disk_data;
foreach my $io (@iostat_system) {
  chomp $io;
#  print $io."\n";
  my @cols=split(' ',$io);

  next unless ($io);
#  if ($cols[0]=~/^device/i) { # what if the device is named device?
   if ($ncols==0 && $cols[0]=~/^device/i) {
      @colnames=map {$_=~s/[^a-zA-Z0-9]//g;$_} @cols;
      $ncols=-1+scalar(@colnames);
#      print join(' ',@colnames)."\n";
      }
  elsif($ncols>0) {
     my $dev=$cols[0];
     for my $i (1..$ncols) { $disk_data{$dev}{$colnames[$i]}=$cols[$i]
+;}
     }
  }

#  use Storable; i dont need this !!!!
  use Data::Dumper;

  $Data::Dumper::Deepcopy=1;
  $Data::Dumper::Purity=1;
  $Data::Dumper::Sortkeys=1;
  $Data::Dumper::Indent=2;

print Dumper(%disk_data);
[download]

edit:dropped storable

edit:fix case of device named device