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

my %results = do
{
		local $/ = ''; # paragraph mode
		map { /TYPE (\S+)/ => 
					{ 
							'cause'  => (/CAUSE (\S+)/ ?$1:'UNDEF'), 
							'effect' => (/AFFECT (\S+)/?$1:'UNDEF'),
					}
		} <DATA>;
};
print Dumper \%results;

__DATA__
TYPE VALUE1 EQUALS MAIN
CAUSE FAIL
AFFECT ERROR
ENDTYPE

##</code><code>##

$VAR1 = {
          'VALUE1' => {
                        'effect' => 'ERROR',
                        'cause' => 'ERROR'   # instead of 'FAIL'
                      }
        };