For lengthy and complex reasons that we will not get into, can there be any reason you cannot begin a 'directory' having a + ?
Observe that it isn't really a directory, it's being planned utilizing a rewriterule
+Note : Like the old-fashioned tilda ~ but I'd rather not use ~ because nobody knows where it's around the keyboard
No you can't utilize it to touch on, generally symbol
+ in URL describes
Have you try with this particular?
rewriterule ^\+helloworld$ /test.html