Command line to build gv_perl is missing PERL_INCLUDES
gv_perl.cpp includes "EXTERN.h" and therefore the compiler must be able to find the location of files installed with perl. Although PERL_INCLUDES is defined during configuration to point to the correct place, it is not included in the set of CPPFLAGS used to compile gv_perl. Consequently, the compilation fails with a 'file not found' error. The attached patch simply adds PERL_INCLUDES to the correct CPPFLAGS and fixes the problem.