From: Daniel DeLorme <dan-ml@...42.com>
Date: 2007-02-28T14:54:50+09:00
Subject: How can I monitor a Regexp?

Because a regular expression can have different behaviors depending on its kcode 
(e.g. behavior of \w) I decided that all my code should specify the kcode 
explicitly (e.g. /\w+/n instead /\w+/). So I tried to set up some hooks to 
monitor the creation of each Regexp and raise an exception if the kcode is 
missing. Like this:

   class Regexp
     alias old_initialize initialize
     def initialize(*args)
       old_initialize(*args)
       raise "NO KCODE!" if kcode.nil?
     end
   end

And it works fine if I use Regexp.new, but in the majority of cases the regexp 
is expressed as a literal and the initialize is NOT EXECUTED.
   > Regexp.new("foobar")
   RuntimeError: NO KCODE!
   > /foobar/
   => /foobar/

So I tried an alternate approach and set the hook into the =~ operator, but same 
problem; the method override is completely ignored:
   class String; def =~(o); raise "S"; end; end
   class Regexp; def =~(o); raise "R"; end; end
   "bar" =~ /bar/  #=> 0
   /foo/ =~ "foo"  #=> 0

So... anyone has any idea how I can tackle that problem?