changing syntax for a forward slash

[Tim Johnson]

Hello:
I am working with a major mode derived from 'scheme-mode.
The forward slash '/' has a significance in the rebol language
that is similar to '.' in python or '->' in perl. 
In rebol. '/' is referred to as the "refinement operator".

for the following function call: append/only
I would like 
append 
to be highlighted as a keyword
but not 
only

The output from describe-syntax shows the following entry:
- .. /                  _       which means: symbol

I take this to mean that the syntax table stores '/' as
a part of the symbol syntax class.

I use the following form as part of font-lock-keywords:
(,(concat "\\<\\(" rebol-functions-regexp "\\)\\>") 
  0 font-lock-keyword-face)

I am unclear as to whether I should be modifying the syntax
table or whether I should be modifying the last argument to
concat 

Any help and/or pointers to documentation is welcome.
Thanks

-- 
Tim Johnson <tim@johnsons-web.com>
      http://www.alaska-internet-solutions.com