Backport Tim's checkin 1.9:

SF bug 418615: regular expression bug in pipes.py.
Obviously bad regexps, spotted by Jeffery Collins.

Lib/pipes.py

@@ -123,10 +123,10 @@ class Template:
         if self.steps and self.steps[-1][1] == SINK:
             raise ValueError, \
                   'Template.append: already ends with SINK'
-        if kind[0] == 'f' and not re.search('\$IN\b', cmd):
+        if kind[0] == 'f' and not re.search(r'\$IN\b', cmd):
             raise ValueError, \
                   'Template.append: missing $IN in cmd'
-        if kind[1] == 'f' and not re.search('\$OUT\b', cmd):
+        if kind[1] == 'f' and not re.search(r'\$OUT\b', cmd):
             raise ValueError, \
                   'Template.append: missing $OUT in cmd'
         self.steps.append((cmd, kind))
@@ -145,10 +145,10 @@ class Template:
         if self.steps and self.steps[0][1] == SOURCE:
             raise ValueError, \
                   'Template.prepend: already begins with SOURCE'
-        if kind[0] == 'f' and not re.search('\$IN\b', cmd):
+        if kind[0] == 'f' and not re.search(r'\$IN\b', cmd):
             raise ValueError, \
                   'Template.prepend: missing $IN in cmd'
-        if kind[1] == 'f' and not re.search('\$OUT\b', cmd):
+        if kind[1] == 'f' and not re.search(r'\$OUT\b', cmd):
             raise ValueError, \
                   'Template.prepend: missing $OUT in cmd'
         self.steps.insert(0, (cmd, kind))