Since we can't tell if the system perl was built with pedantic, we have a problem because we default debug enabled which uses AX_CFLAGS_WARN_ALL_ANSI, For the GNU CC compiler it will be -Wall (and -ansi -pedantic) The result is added to the shellvar being CFLAGS by default.  Which then gets included for building mod_perl, Either way I think this is the correct corse of action to overcome these new builds of mod_perl.