Folks:

Following on from my discovery that the 1.9 version of Pathname is needed 
for Windows, what's the right way to incorporate that file into a 1.8.4 
setup while avoiding disruption?

1. Should I replace the existing pathname.rb?

But what if there's some existing library that depends on the specifics of 
the old one?

2. Should I add pathname.rb with a new name (pathname19.rb)?

... and then require that file (instead of the old one) where I needed it?

It's one thing for my code to specifically require the newer file, but maybe 
some other library I call will use the old one when I really want it to know 
how to deal with Windows paths.  Hmmm.

3. What's the general procedure for even determining whether the new library 
offers compatible methods etc?

Scratching head...

Graham