It isn't much but I've had a stab at documenting (system repl server) so
that I could feel less guilty about suggesting people use it.

Aside from it's sparseness, the two main issues I've had are
1. Under what section of the manual should it be placed, and
2. How to represent complex optional arguments

For now, I have currently placed it in a new subsection of 6.17 (Reading
and Evaluating Scheme Code). I'm not entirely convinced this is the
right place for it, better suggestions welcome.

For 2, I have described the optional in the text, rather than trying to
placing the expression directly in the prototype.

Rough patch is attached.

-- 
Ian Price -- shift-reset.com

"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"