Couple of notes here:

Here are some example books tags:

• <!-- book-offered:1-56592-419-3 -->
• <!-- book-offered:0-7357-0921-1 -->
• <!-- book-wanted:0-201-48567-2 -->
• <!-- book-loaned:1-56592-262-X,user=979 -->
• <!-- book-loaned:1-56592-392-8,user=39362 -->

I would recommend formatting the ISBN number as it looks on the back of the book. This is called 'The Pretty ISBN Format', but in no way actually impacts anything. ISBN numbers are always 10 digits, except for the last character, which may be an upper or lowercase letter 'X'. Any prettifying dashes are stripped when actually manipulating ISBN numbers.

ISBNs contain a publisher code, a country code, and a check digit in them. There is a CPAN module Business::ISBN that is useful for validating ISBN numbers, as far as being legally constructed and having a valid check digit. Alas, there is no CPAN module for interfacing to an ISBN database and returning nicely formatted data for our own purposes.

Someone referenced me to a site that allows ISBN lookups, and returns HTML that is parsable, although it's still pretty ugly. www.isbn.nu is the root site, and a book can be looked up by going to isbn.nu/0764550292/price. The 0764550292 is the ISBN. You don't have to add the /price, but it will re-write the URL to contain it. There don't seem to be any obvious other options than /price.

Here's what NOT to do:

• <!-- book-loaned:0764550292,user=<a href="/index.pl?node=9270&lastnode_id=979">9270</a> -->
• <!-- book-loaned:0-7645-0762-1,user=<a href="/index.pl?node=9270&lastnode_id=979">9270</a> -->

Note that some silly person tried to stuff a URL in there, when it should just be the homenode number of the person the book is lent to. If it's not a valid homenode number, the scanner will kick it out.

And while I think everyone pretty much has in mind lending Perl related books, remember that since it's a simple ISBN, you can also loan your copies of 'McCracken on Fortran', 'Dr. Suess: Green Eggs & Ham', and 'The Kama Sutra'.

--Chris

e-mail jcwren