Is there a particular reason you have to die on a close failure?
I just used die() for illustration purposes, the real module handles it differently, but it must somehow handle errors on close() because they could be real errors with the command run by the pipe, and the user needs to know what's going on.
Is there a particular reason you need a global filehandle? This issue would seem to go away if you use Indirect Filehandles and let the Perl garbage collection resolve the closing.
The file handle is stored within the module and therefore persists until the object of the class that the module implements goes out of scope. In this case, this happens when the child terminates.
I guess my issue is that this is not a "real" error, neither from the user's perspective (who just forks), or from the module owner's perspective (who just opens/closes a pipe), and therefore it shouldn't even be surfaced.