diff --git a/Demo/scripts/update.py b/Demo/scripts/update.py
new file mode 100755
index 0000000..e8f6283
--- /dev/null
+++ b/Demo/scripts/update.py
@@ -0,0 +1,91 @@
+#! /usr/local/bin/python
+
+# Update a bunch of files according to a script.
+# The input file contains lines of the form <filename>:<lineno>:<text>,
+# meaning that the given line of the given file is to be replaced
+# by the given text.  This is useful for performing global substitutions
+# on grep output: 
+
+import os
+import sys
+import regex
+
+pat = '^\([^: \t\n]+\):\([1-9][0-9]*\):'
+prog = regex.compile(pat)
+
+class FileObj:
+	def __init__(self, filename):
+		self.filename = filename
+		self.changed = 0
+		try:
+			self.lines = open(filename, 'r').readlines()
+		except IOError, msg:
+			print '*** Can\'t open "%s":' % filename, msg
+			self.lines = None
+			return
+		print 'diffing', self.filename
+
+	def finish(self):
+		if not self.changed:
+			print 'no changes to', self.filename
+			return
+		try:
+			os.rename(self.filename, self.filename + '~')
+			fp = open(self.filename, 'w')
+		except (os.error, IOError), msg:
+			print '*** Can\'t rewrite "%s":' % self.filename, msg
+			return
+		print 'writing', self.filename
+		for line in self.lines:
+			fp.write(line)
+		fp.close()
+		self.changed = 0
+
+	def process(self, lineno, rest):
+		if self.lines is None:
+			print '(not processed): %s:%s:%s' % (
+				  self.filename, lineno, rest),
+			return
+		i = eval(lineno) - 1
+		if not 0 <= i < len(self.lines):
+			print '*** Line number out of range: %s:%s:%s' % (
+				  self.filename, lineno, rest),
+			return
+		if self.lines[i] == rest:
+			print '(no change): %s:%s:%s' % (
+				  self.filename, lineno, rest),
+			return
+		if not self.changed:
+			self.changed = 1
+		print '%sc%s' % (lineno, lineno)
+		print '<', self.lines[i],
+		print '---'
+		self.lines[i] = rest
+		print '>', self.lines[i],
+
+def main():
+	if sys.argv[1:]:
+		try:
+			fp = open(sys.argv[1], 'r')
+		except IOError, msg:
+			print 'Can\'t open "%s":' % sys.argv[1], msg
+			sys.exit(1)
+	else:
+		fp = sys.stdin
+	curfile = None
+	while 1:
+		line = fp.readline()
+		if not line:
+			if curfile: curfile.finish()
+			break
+		n = prog.match(line)
+		if n < 0:
+			print 'Funny line:', line,
+			continue
+		filename, lineno = prog.group(1, 2)
+		if not curfile or filename <> curfile.filename:
+			if curfile: curfile.finish()
+			curfile = FileObj(filename)
+		curfile.process(lineno, line[n:])
+
+main()