Provided a script printenv.cgi exists in the logical directory
/juttacgi,
/juttacgi/printenv.cgi/animal/mammal/white?has-hornswill execute it with the
PATH_INFO environment variable
containing the string "animal/mammal/white",
while the QUERY_STRING variable will be set
to "has-horns".
QUERY_STRING makes fields in a fill-out form work,
and the search query field that browsers automatically generate when
a document is marked as ``indexable'' by
containing the <isindex> tag.
After a user has entered a search query (or pressed the ``submit'' button
in a form), the browser appends a ? to the document URL (or
form action), followed by the search string (or the names and contents
of the fields in the form, respectively), and then loads the resulting
URL.
As long as I'm not using forms or <isindex> queries,
there's really no particular reason to place information in the
PATH_INDEX part or in the QUERY_STRING;
I needed some way to tell one parameter from the others, so I chose
to do it the natural way and use the distinction that CGI already
offers.