diff --git a/ChangeLog b/ChangeLog
index c8c6b804fd..0ec75bbdef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Jul 26 22:45:18 2008  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
+
+	* sample/exyacc.rb: fixed NoMethodError(Kernel#sub!).
+	  replaced use of special variables with explicit IO 
+	  operations.
+
 Sat Jul 26 21:17:18 2008  Masaki Suketa  <masaki.suketa@nifty.ne.jp>
 
 	* ext/win32ole/win32ole.c (Init_win32ole): add
diff --git a/sample/exyacc.rb b/sample/exyacc.rb
index 5818825e25..c96ebfd676 100644
--- a/sample/exyacc.rb
+++ b/sample/exyacc.rb
@@ -2,21 +2,19 @@
 # usage: exyacc.rb [yaccfiles]
 # this is coverted from exyacc.pl in the camel book
 
-$/ = nil
-
-while gets()
-  sbeg = $_.index("\n%%") + 1
-  send = $_.rindex("\n%%") + 1
-  $_ = $_[sbeg, send-sbeg]
-  sub!(/.*\n/, "")
-  gsub!(/'\{'/, "'\001'")
-  gsub!(/'\}'/, "'\002'")
-  gsub!(%r{\*/}, "\003\003")
-  gsub!(%r{/\*[^\003]*\003\003}, '')
-  while gsub!(/\{[^{}]*\}/, ''); end
-  gsub!(/'\001'/, "'{'")
-  gsub!(/'\002'/, "'}'")
-  while gsub!(/^[ \t]*\n(\s)/, '\1'); end
-  gsub!(/([:|])[ \t\n]+(\w)/, '\1 \2')
-  print $_
+ARGF.each(nil) do |source|
+  sbeg = source.index("\n%%") + 1
+  send = source.rindex("\n%%") + 1
+  grammer = source[sbeg, send-sbeg]
+  grammer.sub!(/.*\n/, "")
+  grammer.gsub!(/'\{'/, "'\001'")
+  grammer.gsub!(/'\}'/, "'\002'")
+  grammer.gsub!(%r{\*/}, "\003\003")
+  grammer.gsub!(%r{/\*[^\003]*\003\003}, '')
+  while grammer.gsub!(/\{[^{}]*\}/, ''); end
+  grammer.gsub!(/'\001'/, "'{'")
+  grammer.gsub!(/'\002'/, "'}'")
+  while grammer.gsub!(/^[ \t]*\n(\s)/, '\1'); end
+  grammer.gsub!(/([:|])[ \t\n]+(\w)/, '\1 \2')
+  print grammer
 end