TIMTOW...

use strict;
use warnings;
use Data::Dumper;

local $/;
my %data = (map{unpack 'x19A5x25A*', $_}<DATA>);
print Dumper(\%data);


__DATA__
Data Collected for SA120:Prct Dirty Cache Pages =            0


Data Collected for SA121:Prct Dirty Cache Pages =            1


Data Collected for SA122:Prct Dirty Cache Pages =            0


Data Collected for SA220:Prct Dirty Cache Pages =            0


Data Collected for SA221:Prct Dirty Cache Pages =            0


Data Collected for SA222:Prct Dirty Cache Pages =            17
[download]

OUTPUT:

$VAR1 = {
          ' SA220' => '            0',
          ' SA221' => '            0',
          ' SA122' => '            0',
          ' SA222' => '            17',
          ' SA121' => '            1',
          ' SA120' => '            0'
        };
[download]

update :

/.+(SA\d{3}).+?(\d+)(?{$data{$1}=$2})/ for <DATA>
[download]

HTH,
PooLpi