Proposal for exception handling

["Guillermo J. Rozas" <gjr@martigny.ai.mit.edu>]

I agree with Stephen Adams.  The hard part about a condition system is
what is signalled, with what additional data, and when.

The rest is trivial.

After all, I could just (this is not a serious proposal, just pointing
out, along with KMP that control structure is not the issue at all)

(let ((old-raise raise))
  (fluid-let ((raise (lambda (condition . data)
		       (if (my-condition? condition)
			   <handle the condition>
			   (apply old-raise condition data)))))
    <protected body>))