Problem with double-quoted expressions in language definition

I'm using source-highlight version 3.1.8 on OS X 10.11.3.
(I installed it using homebrew).


I am writing a language definition file for Forth and I cannot get 
double-quoted expressions to work. Perhaps I am misunderstanding something.

According to my understanding of the documentation, if I double-quote 
keywords then they should only match if they are surrounded by a word 
boundary, i.e. they should not match internally to an alphanumeric string.

Below is a snippet from my forth.lang:

keyword = "i",
  "j",
  "k",
  "for",
  "do",
  "of"

But when I run source-highlight on a sample Forth file, it highlights 
the "do" in "does>" and the "i" in "trial", etc.

I've posted the complete forth.lang file to 
http://bluedino.net/downloads/forth.lang and a sample image of the 
output to http://bluedino.net/downloads/forthlisting.png. Note that I am 
also using a custom style file so that I can use custom language 
elements (for completeness I've uploaded it to 
http://bluedino.net/downloads/forth.style)	.

Any help is appreciated!

Thanks,

Matt