Ruby 1.9 regex as a hash key

Question

I am trying this example myhash = {/(\d+)/ => "hello"} with ruby 1.9.2p136 (2010-12-25) [i386-mingw32].
It doesn't work as expected (edit: as it turned out it shouldn't work as I was expecting):

irb(main):004:0> myhash = {/(\d+)/ => "hello"}
=> {/(\d+)/=>"Hello"}
irb(main):005:0> myhash[2222]
=> nil
irb(main):006:0> myhash["2222"]
=> nil

In Rubular which is on ruby1.8.7 the regex works.
What am I missing?

Answer 1

You can put Jean's answer in a default_proc

MAP = {
  /1/ => "one",
  /2/ => "two",
  /\d/ => "number"
}

MAP.default_proc = lambda do |hash, lookup|
  hash.each_pair do |key, value|
    return value if key =~ lookup
  end
  return nil
end

p MAP["2"] #=> "two"
p MAP[44] #=> "number"