Blah blah blah about the overall design, and the basic structure
    of the program is as follows:
    <<foo.pl>>=
    #!/usr/bin/perl -w
    use strict;
    <<load modules>>
    <<initialize data structures>>
    <<accept user input>>
    <<perform analysis>>
    <<error checking>>
    <<foo.pod>>
    @

##</code><code>##

       --- tangle ----> foo.pl
      |
 foo.nw
      |
       --- weave -----> foo.tex ----> latex foo ----> foo.dvi
             |                    |
             |                     -> pdflatex foo -> foo.pdf
              --------> foo.html