Can't exec "pkg-config": No such file or directory at Makefile.PL line 6. Use of uninitialized value in scalar chomp at Makefile.PL line 6. Can't exec "pkg-config": No such file or directory at Makefile.PL line 7. Use of uninitialized value in scalar chomp at Makefile.PL line 7. cannot find opencv library. at Makefile.PL line 8.