diff --git a/include/boost/preprocessor/expr_if.hpp b/include/boost/preprocessor/expr_if.hpp
index b748264..a86ae10 100644
--- a/include/boost/preprocessor/expr_if.hpp
+++ b/include/boost/preprocessor/expr_if.hpp
@@ -13,7 +13,9 @@
  * See http://www.boost.org for most recent version.
  */
 
-#include <boost/preprocessor/detail/cat.hpp>
+// pm:  not necessary if using manual delay
+// #include <boost/preprocessor/detail/cat.hpp>
+
 #include <boost/preprocessor/logical/bool.hpp>
 
 /** <p>Expands to <code>EXPR</code> if <code>COND != 0</code> and to nothing if <code>COND == 0</code>.</p>
@@ -27,7 +29,10 @@
   <li>BOOST_PP_IF()</li>
 </ul>
 */
-#define BOOST_PP_EXPR_IF(COND,EXPR) BOOST_PP_DETAIL_CAT2(BOOST_PP_EXPR_IF,BOOST_PP_BOOL(COND))(EXPR)
+#define BOOST_PP_EXPR_IF(COND,EXPR) BOOST_PP_EXPR_IF_BOOL(BOOST_PP_BOOL(COND),EXPR) // original:  BOOST_PP_DETAIL_CAT2(BOOST_PP_EXPR_IF,BOOST_PP_BOOL(COND))(EXPR)
+
+#define BOOST_PP_EXPR_IF_BOOL(COND,EXPR) BOOST_PP_EXPR_IF_BOOL_DELAY(COND,EXPR)
+#define BOOST_PP_EXPR_IF_BOOL_DELAY(COND,EXPR) BOOST_PP_EXPR_IF##COND(EXPR)
 
 #define BOOST_PP_EXPR_IF0(E)
 #define BOOST_PP_EXPR_IF1(E) E
diff --git a/include/boost/preprocessor/if.hpp b/include/boost/preprocessor/if.hpp
index 1a6266a..3e7f296 100644
--- a/include/boost/preprocessor/if.hpp
+++ b/include/boost/preprocessor/if.hpp
@@ -13,7 +13,9 @@
  * See http://www.boost.org for most recent version.
  */
 
-#include <boost/preprocessor/detail/cat.hpp>
+// pm:  not necessary if using manual delay
+// #include <boost/preprocessor/detail/cat.hpp>
+
 #include <boost/preprocessor/logical/bool.hpp>
 
 /** <p>Expands to <code>THEN</code> if <code>COND != 0</code> and <code>ELSE</code> if
@@ -33,7 +35,11 @@
   <li><a href="../../test/preprocessor_test.cpp">preprocessor_test.cpp</a></li>
 </ul>
 */
-#define BOOST_PP_IF(COND,THEN,ELSE) BOOST_PP_DETAIL_CAT2(BOOST_PP_IF,BOOST_PP_BOOL(COND))(ELSE,THEN)
-#define BOOST_PP_IF0(E,T) E
-#define BOOST_PP_IF1(E,T) T
+#define BOOST_PP_IF(COND,THEN,ELSE) BOOST_PP_IF_BOOL(BOOST_PP_BOOL(COND),THEN,ELSE) // original:  BOOST_PP_DETAIL_CAT2(BOOST_PP_IF,BOOST_PP_BOOL(COND))(ELSE,THEN)
+
+#define BOOST_PP_IF_BOOL(COND,THEN,ELSE) BOOST_PP_IF_BOOL_DELAY(COND,THEN,ELSE)
+#define BOOST_PP_IF_BOOL_DELAY(COND,THEN,ELSE) BOOST_PP_IF##COND(THEN,ELSE)
+
+#define BOOST_PP_IF0(T,E) E // BOOST_PP_IF0(E,T) E
+#define BOOST_PP_IF1(T,E) T // BOOST_PP_IF1(E,T) T
 #endif
diff --git a/include/boost/preprocessor/logical/bool.hpp b/include/boost/preprocessor/logical/bool.hpp
index 5f41ee8..5234f1b 100644
--- a/include/boost/preprocessor/logical/bool.hpp
+++ b/include/boost/preprocessor/logical/bool.hpp
@@ -13,7 +13,8 @@
  * See http://www.boost.org for most recent version.
  */
 
-#include <boost/preprocessor/detail/cat.hpp>
+// pm:  not necessary if using manual delay
+// #include <boost/preprocessor/detail/cat.hpp>
 
 /** <p>Expands to <code>0</code> if <code>X == 0</code> and <code>1</code> if <code>X != 0</code>.</p>
 
@@ -21,7 +22,8 @@
 
 <p>For example, <code>BOOST_PP_BOOL(3)</code> expands to <code>1</code>.</p>
 */
-#define BOOST_PP_BOOL(X) BOOST_PP_DETAIL_CAT2(BOOST_PP_BOOL,X)
+#define BOOST_PP_BOOL(X) BOOST_PP_BOOL_DELAY(X) // original:  BOOST_PP_DETAIL_CAT2(BOOST_PP_BOOL,X)
+#define BOOST_PP_BOOL_DELAY(X) BOOST_PP_BOOL##X
 
 /* BOOL can be implemented in O(1) tokens using saturated ADD & SUB.
  * Unfortunately, it would result in significantly slower preprocessing.