my $flag = 0;		# TRUE when in a sub header or sub-sub header

my @rry = <DATA>;
for my $rry(@rry) {
	if ( $rry =~ /\A={3,4}sub.*?={3,4}$/ ) {
		$flag = 1;
		print $rry . "\n";
		next;
	} if ( $rry =~ /\A[^=].*/ && $flag == 1 ) {
		print $rry . "\n";
	} else {
		$flag=0;
		next;
	}
}


##</code><code>##

===sub header===



[[testing]]



====sub-sub header====



bla bla



===sub header===



[[testing]]



sub-sub header



bla bla