This website uses a rewrite-rule to send anything and everything to a CGI script (CGI::Application). The site uses the "ActionDispatch" plugin, which relies upon $ENV{'PATH_INFO'} to find the routine to call.

There is a RewriteRule that sends “anything that does not correspond to a physical file” to the cgi-bin script, and all that seems to be working as I expect.

The very odd thing, at least to me at least right now, is that I'm seeing this environment-variable showing up as undef ... but $ENV{'REQUEST_URI'} is properly defined. It contains the value that I intuitively expected. I am quite at a loss to explain why the other value is “missing entirely.”

Furthermore, it seems to be that way no matter what URI-string I use. (The “default” handler uses REQUEST_URI, therefore it works fine.)

An example of the sort of URI that comes up empty is... well, anything...   http://www.foo.bar/wonderfulproduct/info

In that situation, REQUEST_URI will be /wonderfulproduct/info and PATH_INFO will be undef. And I really don't know why it's undef.

I'm also contemplating exactly what to do about it... How might I diagnose the situation further, and then, much more to the point, make it go away? Categorically, I prefer not to “bypass” a problem until first I understand why it's happening, because who knows, it might be a symptom of a deeper issue that's just going to come back.