Retrieving values from Env in mod_esi or webtools

[Tim Williams]

A complete noob question, but how exactly do I get values (e.g.
path_info) from inside the callback?  From the docs, I thought it was
a list of tuples, which I thought would make it accessible via
lists:keyfind, but I've had no luck.  So far, all the examples I've
found only show how to print everything with io_lib but not how to
access the values by key...

Thanks,
--tim