Extract a method or a function.

This is Refactoring / code cleanup.

See:

* https://refactoring.com/catalog/extractMethod.html

* https://en.wikipedia.org/wiki/Code_refactoring

* https://www.refactoring.com/

* https://www.joelonsoftware.com/2002/01/23/rub-a-dub-dub/

Some small optimisations may have slipped in as well.

fortune-mod/CMakeLists.txt

@@ -292,6 +292,11 @@ ENDIF()
 
 CHECK_INCLUDE_FILE("regex.h" HAVE_REGEX_H)
 
+MACRO(_fortune__enable_regex)
+    ADD_DEFINITIONS("-DHAVE_REGEX_H")
+    ADD_DEFINITIONS("-DPOSIX_REGEX")
+ENDMACRO()
+
 IF (USE_PCRE)
     FIND_PACKAGE (PkgConfig REQUIRED)
     pkg_check_modules(PCRE2 REQUIRED libpcre2-posix)
@@ -300,11 +305,9 @@ IF (USE_PCRE)
     add_definitions (${PCRE2_CFLAGS_OTHER})
     TARGET_LINK_LIBRARIES("fortune" ${PCRE2_LIBRARIES})
     ADD_DEFINITIONS("-DHAVE_PCRE2")
-    ADD_DEFINITIONS("-DHAVE_REGEX_H")
-    ADD_DEFINITIONS("-DPOSIX_REGEX")
+    _fortune__enable_regex()
 ELSEIF (HAVE_REGEX_H)
-    ADD_DEFINITIONS("-DHAVE_REGEX_H")
-    ADD_DEFINITIONS("-DPOSIX_REGEX")
+    _fortune__enable_regex()
 ENDIF()
 
 ADD_DEFINITIONS("-DHAVE_STDBOOL")