I believe there is a bug in rifle, on line 198.
The 'lower()' conversion should be left out, i.e. as in the diff below:

198c198
<             extension = os.path.basename(files[0]).rsplit('.', 1)[-1].lower()
---
>             extension = os.path.basename(files[0]).rsplit('.', 1)[-1]

(or, if you prefer it in patch format:

--- rifle.old   2014-03-17 21:51:55.000000000 +0000
+++ rifle.new   2014-11-07 07:52:13.751158088 +0000
@@ -195,7 +195,7 @@
         argument = rule[1] if len(rule) > 1 else ''

         if function == 'ext':
-            extension = os.path.basename(files[0]).rsplit('.', 1)[-1].lower()
+            extension = os.path.basename(files[0]).rsplit('.', 1)[-1]
             return bool(re.search('^(' + argument + ')$', extension))
         elif function == 'name':
             return bool(re.search(argument, os.path.basename(files[0])))

)

The 'extension' variable seems to hold the actual file extension that will be checked against the list of regexes specified after the 'ext' keyword in the 'rifle.conf'. If the regex extension matches, the given command action is executed. For example:

ext 7z|ace|ar|arc|bz2?|cab|cpio|cpt|deb|dgc|dmg|gz,  has als     = als -- "$@" | "$PAGER"

As it is now, the bug does not allow rifle to act on extensions/regexes containing any upper case letters since the 'extension' var will always be lowercase. For example, something like 'archive.tar.Z' cannot be simply matched by adding to the above list of regex alternatives just 'Z'. (yes, it will match if you add a single lowercase 'z', but that's not really the same extension).