CPPFLAGS=-Dre_max_failures=re_max_failures2: The CPPFLAGS variable is a variable that's read by the cpp program (C PreProcessor). The value of this variable tells the preprocessor to replace every instance of re_max_failures it finds by re_max_failures2 before handing the source file to the compiler itself for compilation. This package has problems linking statically on certain platforms (depending on the Glibc version used on that system) and this construction fixes that problem.