Issue: PATHNAME-EXTENSIONS (Version 1)

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

This sounds reasonable at first, but I was unable to think of any
way that a correct portable program could use it.  If there was a
use for it, I couldn't convince myself that a single yes/no distinction
was sufficient; some extensions to Common Lisp pathname semantics
might be handled by a CL function that the user program was going to
call, thus they wouldn't interfere with use of an "extended" pathname.
Indeed, why isn't this true of all such extensions?

I think you need to supply a real example.