diff --git a/ChangeLog b/ChangeLog
index 676dcb18f8..ba8d508994 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -140,6 +140,11 @@ Sat Sep  6 06:05:09 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 	  a patch from Tadashi Saito <shiba at mail2.accsnet.ne.jp>
 	  in [ruby-dev:36102].
 
+Sat Sep  6 04:44:06 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* proc.c (Init_Proc): add '===' operator to use procs in when
+	  clause of the case statement.  inspired by <http://www.aimred.com/news/developers/2008/08/14/unlocking_the_power_of_case_equality_proc/>.
+
 Sat Sep  6 03:18:17 2008  Tanaka Akira  <akr@fsij.org>
 
 	* transcode.c (allocate_converted_string): add arguments for a buffer
diff --git a/proc.c b/proc.c
index 710ab065d1..56c51ccabb 100644
--- a/proc.c
+++ b/proc.c
@@ -466,12 +466,14 @@ proc_lambda(void)
  *  call-seq:
  *     prc.call(params,...)   => obj
  *     prc[params,...]        => obj
+ *     prc.(params,...)       => obj
  *  
  *  Invokes the block, setting the block's parameters to the values in
  *  <i>params</i> using something close to method calling semantics.
  *  Generates a warning if multiple values are passed to a proc that
  *  expects just one (previously this silently converted the parameters
- *  to an array).
+ *  to an array).  Note that prc.() invokes prc.call() with the parameters
+ *  given.  It's a syntax sugar to hide "call".
  *
  *  For procs created using <code>Kernel.proc</code>, generates an
  *  error if the wrong number of parameters
@@ -494,6 +496,14 @@ proc_lambda(void)
  *     	from prog.rb:5
  */
 
+/*
+ *  call-seq:
+ *     prc === obj   => obj
+ *  
+ *  Invokes the block, with <i>obj</i> as the block's parameter.  It is
+ *  to allow a proc object to be a target of when clause in the case statement.
+ */
+
 static VALUE
 proc_call(int argc, VALUE *argv, VALUE procval)
 {
@@ -1745,6 +1755,7 @@ Init_Proc(void)
     rb_define_singleton_method(rb_cProc, "new", rb_proc_s_new, -1);
     rb_define_method(rb_cProc, "call", proc_call, -1);
     rb_define_method(rb_cProc, "[]", proc_call, -1);
+    rb_define_method(rb_cProc, "===", proc_call, -1);
     rb_define_method(rb_cProc, "yield", proc_call, -1);
     rb_define_method(rb_cProc, "to_proc", proc_to_proc, 0);
     rb_define_method(rb_cProc, "arity", proc_arity, 0);