README: revise bullet 3.

1 files changed, 14 insertions, 6 deletions

diff --git a/README.md b/README.md
index 08fce62..5e16a7f 100644
--- a/README.md
+++ b/README.md
@@ -51,12 +51,20 @@ and go get it!
     files, which easily find each other in the same directory or relative
     path. Or macros, for some syntactic sugars.
 
-3.  Though GNU Awk has `@include`, that feature provides no preprocessor
-    features and works with GNU Awk only. `cppawk` calls `gawk`, but can
-    easily be tweaked to target any Awk; any Awk can have file inclusion.
-    There is the possibility of using `#ifdef` to make code
-    work on different Awks from one file. (The default cppawk installation uses
-    gawk, and also defines `__gawk__` as 1, which you can test for.)
+3.  `cppawk` calls `gawk`, but can easily be tweaked to target any Awk; any Awk
+    can have file inclusion.  There is the possibility of using `#ifdef` to
+    make code work with different Awks, using their nonportable constructs:
+
+        #if __gawk__
+        GNU Awk specific code
+        #else
+        ...
+        #endif
+
+    The default cppawk installation uses gawk, and also defines `__gawk__`
+    with a value of `1`. (If an installation of `cppawk` is prepared which uses
+    a different awk, it is strongly recommended to define a different symbol to
+    `1`, based on the name: `__mawk__`, and so forth.)
 
 4.  Comments. Awk has no comments that don't end at the end of
     the line; `cppawk` gives you `/*...*/`.