MSGLOG_DIRECTORY_MODE optional* mode for message log directory
MV_COMMAND system path to mv command
NO_SYMLINK optional install doesn't make 'exim" symlink
-PCRE_CFLAGS system compile flags for PCRE library
+PCRE_CONFIG system* use pcre-config for PCRE support
+PCRE_LIBS system* library for using PCRE
PERL_CC system* compiler for Perl interface code
PERL_CCOPTS system* flags for same
PERL_COMMAND system path to Perl