From: Charles Oliver Nutter <headius@...>
Date: 2009-06-11T03:44:53+09:00
Subject: Re: Match data variables

On Wed, Jun 10, 2009 at 10:03 AM, Lars
Christensen<larschbelunktumdk@gmail.com> wrote:
> I understand that $~ and its friends ($&, $1, ...) are method local, but:
>
> Can a custom method mimic the behaviour of String#match, String#=~ etc
> and set the match data for the caller?

No. There is no way (without a supergross hack like using
set_trace_func or something).

This is one of my strongest arguments against those variables and
methods that manipulate them, since they have this extra "magic"
behavior that you can't mimic in Ruby code (without
implementation-specific hacks). For this reason no methods that
access/modify $~ or $_ should ever be wrapped or aliased, and we even
warn against aliasing in JRuby since we use the presence of those
methods to make some optimization decisions.

I wish $~ and $_ were not in the language.

- Charlie