The following works for your given sample data, but I'll be the first to admit that it isn't a very good solution.

#!/usr/bin/perl -w
use strict;
use Data::Dumper::Simple;

my %data;

while (<DATA>) {
    chomp;
    my @fields = split /=/;
    my $depth = scalar @fields;
    if ($depth == 1) {
        $data{$fields[0]} = undef;
    }
    elsif ($depth == 2) {
        $data{$fields[0]} = $fields[1];
    }
    elsif ($depth == 3) {
        $data{$fields[0]}{$fields[1]} = $fields[2];
    }
}

print Dumper(%data);

__DATA__
a = ID = 1234
b=Gadens_Melb
c=
d=
e=2006-03-27 15:10:06
f= ContactSensor:INPUT2
g=Critical
h=Event-101 fatal stack error on PRI 001
[download]

Output:

%data = (
          'e' => '2006-03-27 15:10:06',
          'c' => undef,
          'a ' => {
                    ' ID ' => ' 1234'
                  },
          'h' => 'Event-101 fatal stack error on PRI 001',
          'g' => 'Critical',
          'b' => 'Gadens_Melb',
          'd' => undef,
          'f' => ' ContactSensor:INPUT2'
        );
[download]

Cheers,
Darren :)