Here is a quick bit of "one-linery" that appears to work much as requested (at least with both the sample data you provided and a status.dat file from a Nagios system I have access to). It creates a hash, loads the values (with the type of entry in a TYPE field), and displays the entry using Data::Dumper. (Code also includes a "one-liner" that generates the sample data you provided.)

Code:

perl -Mstrict -Mwarnings -le '
sub tab { 
  return q{ } x 4; 
} 
foreach my $s ( 
  q(hoststatus {), 
  tab . q{host_name=AAA1}, 
  tab . q{modified_attributes=0}, 
  tab . q{check_command=check-host-alive}, 
  tab . q{check_period=24x7}, 
  tab . q{notification_period=24x7}, 
  tab . q{check_interval=5.000000}, 
  tab . q{retry_interval=1.000000}, 
  tab . q(}), 
  q{}, 
  q(servicestatus {), 
  tab . q{host_name=AAA1}, 
  tab . q{plugin_output=eth0:UP, eth2:UP, eth3:UP, eth1:UP:4 UP: OK}, 
  tab . q(}) ) 
{ 
  print $s; 
}
' \
| \
perl -Mstrict -Mwarnings -MData::Dumper -lne '
use vars qw(%s); 
BEGIN{ 
  $Data::Dumper::Deepcopy 
    = $Data::Dumper::Sortkeys 
    = 1; 
}; 
chomp; 
if ( m/\}/ ) { 
  print Data::Dumper->Dump( [ \%s, ], [ qw( *s ) ] ); 
  %s = (); 
} 
next if ( m/^\s*$/imsx ); 
$s{TYPE} = $1 if ( m/^\s*(\S+)\s*\{/imsx ); 
$s{$1} = $2 if ( m/^\s+([^=]+)=(.+)$/imsx ); 
'
[download]

Output:

%s = (
       'TYPE' => 'hoststatus',
       'check_command' => 'check-host-alive',
       'check_interval' => '5.000000',
       'check_period' => '24x7',
       'host_name' => 'AAA1',
       'modified_attributes' => '0',
       'notification_period' => '24x7',
       'retry_interval' => '1.000000'
     );

%s = (
       'TYPE' => 'servicestatus',
       'host_name' => 'AAA1',
       'plugin_output' => 'eth0:UP, eth2:UP, eth3:UP, eth1:UP:4 UP: OK
+'
     );
[download]

Hope that helps.

Update: 2016-04-01
Quote mentions of "one-liner", as the code was written over multiple lines for readability.

Update: 2016-04-01
To answer the question in Re^2: Parsing nagios status.dat, instead of the first perl code (before the pipe ('|' character)), you would instead put something like cat /path/to/status.dat | perl .... (If you have questions regarding execution of scripts or "one-liners", you may wish to speak to your local sysadmin or help desk.)