As near as I can tell, every time I try to build the module with cpan it creates a new directory for the code

So - what's the process for patching the file and building it? Do I just run make install in the .cpan/build/XML-Atom-0.42-4 directory or is there something more involved that I need to do?

Go into one of those directories, change that one line as mentioned in the issue.

perl Makefile.PL
make
make test
make install
[download]

Slight modification to instructions:
1. Make code change to XML-Atom-0.42-6/t/31-external-entities-libxml.t(from coolo here)
2. Build code:

   cd ~/.cpan/build/XML-Atom-0.42-6
   perl Build.PL
   setenv PERL5LIB ".:$PERL5LIB"
   ./Build
   ./Build test
   ./Build install
   [download]

   Note: the '-6' on the path above is environment-specific as cpan creates a new directory every time you try to build the module with cpan

Now I need to see how the rest of my build attempt goes...

Thanks!!!