Others have given you good suggestions already. I just wanted to show that you could use the Text::xSV::Slurp module to create the HoH structure for you. The whitespace separated data would be a problem for this module, so you would need your input data to be in a delimited format for this approach to work (like csv shown below). BrowserUK has shown how to deal with the whitespace separated data that you have. I would encourage you to become very familiar with how to use hashes in perl before resorting to a module to do the work for you, since they are such an important feature of perl.

This code:

#!/usr/bin/env perl

use strict;
use warnings;

use Text::xSV::Slurp;

my $hoh = xsv_slurp(
    \*DATA,
    shape    => 'hoh',
    key      => 'Subsystem',
);

use Data::Dumper;

print Dumper $hoh;

exit;

__DATA__
Subsystem,Group,PID,Status
inetd,tcpip,2424886,active
xntpd,tcpip,3473550,active
rwhod,tcpip,,inoperative
snmpd,tcpip,,inoperative
aixmibd,tcpip,,inoperative
hostmibd,tcpip,,inoperative
snmpmibd,tcpip,,inoperative
[download]

Gives the output:

$VAR1 = {
          'inetd' => {
                       'Group' => 'tcpip',
                       'Status' => 'active',
                       'PID' => '2424886'
                     },
          'hostmibd' => {
                          'Group' => 'tcpip',
                          'Status' => 'inoperative',
                          'PID' => ''
                        },
          'snmpmibd' => {
                          'Status' => 'inoperative',
                          'PID' => '',
                          'Group' => 'tcpip'
                        },
          'aixmibd' => {
                         'PID' => '',
                         'Status' => 'inoperative',
                         'Group' => 'tcpip'
                       },
          'snmpd' => {
                       'Group' => 'tcpip',
                       'Status' => 'inoperative',
                       'PID' => ''
                     },
          'xntpd' => {
                       'Group' => 'tcpip',
                       'Status' => 'active',
                       'PID' => '3473550'
                     },
          'rwhod' => {
                       'Group' => 'tcpip',
                       'Status' => 'inoperative',
                       'PID' => ''
                     }
        };
[download]