[plt-scheme] Re: on 371, requiring SRFI 19 yields an error

'Twas pilot error -- I had some weird modifications to my source which
I've forgotten about. Reverting those changes made everything work.
Sorry to raise an alarm; nothing to see here; go about your business.
-- 
In the practice of computing, where we have so much latitude for
making a mess of it, mathematical elegance is not a dispensable
luxury, but a matter of life and death.
        -- Edsger W. Dijkstra: My Hopes of Computing Science (EWD  709)
        http://www.cs.utexas.edu/users/EWD/ewd07xx/EWD709.PDF