Routing Code - question

In routing.rb, what is the purpose of the following piece of code:

class Regexp #:nodoc:
  def number_of_captures
    Regexp.new("|#{source}").match('').captures.length
  end

Does this method not always return 0? It's always going to match ''
with the blank spot before the | and therefore will have no captures.

Regexp.new("|(.)").match("a").captures.length

=> 1

Just responding to see KC's response since Google Groups is borked and
not showing the last response in each thread.