Mac OS X uses the HFS+ filesystem by default (can 
also use UFS).  HFS+ is case-preserving but case-
insensitive.  This limitation causes a namespace 
conflict at compile time.  As a result, the PEAR 
component won't compile, which leads to a general 
make failure.

In the pear subdirectory, there is a source directory 
called PEAR.  When make tries to create the file pear at 
the same level from pear.in, it can't because the name 
is already taken by the directory.

My solution was to rename the PEAR directory and edit 
references to it in Makefile.in

None of the other directories in pear seem to have this 
problem.