Nifty Ruby Unicode codepoints utility

I recently learned about the Module.const_missing method for lazily computed constants, and came up with this Unicode utility module to try it out.

#
# This module lazily defines constants of the form Uxxxx for all Unicode
# codepoints from U0000 to U10FFFF. The value of each constant is the
# UTF-8 string for the codepoint.
# Examples:
#   copyright = Unicode::U00A9
#   euro = Unicode::U20AC
#   infinity = Unicode::U221E
#
module Unicode
  def self.const_missing(name)  
    # Check that the constant name is of the right form: U0000 to U10FFFF
    if name.to_s =~ /^U([0-9a-fA-F]{4,5}|10[0-9a-fA-F]{4})$/
      # Convert the codepoint to an immutable UTF-8 string,
      # define a real constant for that value and return the value
      const_set(name, [$1.to_i(16)].pack("U").freeze)
    else  # Raise an error for constants that are not Unicode.
      raise NameError, "Uninitialized constant: Unicode::#{name}"
    end
  end
end