As AppleFritter said, it seems you would need an array of hash references. the code below would accomplish that.

#!/usr/bin/perl
use strict;
use warnings;

my @data;
my $keys = 'Log Name|Source|Date|Event ID';
{
    local $/ = '';
    while (<DATA>) {
                chomp;
        my %temp = /($keys): (.+)/g;
        if (/^\s+Description:\s+(.+)\z/sm) {
            $temp{description} = $1;    
        }
        push @data, \%temp;
    }    
}
use Data::Dumper; print Dumper \@data;
[download]

Using the data you posted, it dumps:

$VAR1 = [
          {
            'Event ID' => '7320',
            'Log Name' => 'Microsoft-Windows-GroupPolicy/Operational',
            'Source' => 'Microsoft-Windows-GroupPolicy',
            'description' => 'Error: Computer determined to be not in 
+a site. Error code 0x77F.',
            'Date' => '2014-06-26T13:58:04.290'
          },
          {
            'Event ID' => '7320',
            'Log Name' => 'Microsoft-Windows-GroupPolicy/Operational',
            'Source' => 'Microsoft-Windows-GroupPolicy',
            'description' => 'Error: Computer determined to be not in 
+a site. Error code 0x77F.',
            'Date' => '2014-06-26T12:32:30.009'
          }
        ];
[download]

Chris