From: mike leonard <mikeleonard@...>
Date: 2008-03-21T21:59:55+09:00
Subject: A question involving variable evaluation

Hello friends,

I'm working on some code that will iterate through an array of regex
patterns and values, returning a value when the corresponding regex is
matched:

the_string = "foobar"
patterns_and_values = [[/(foo)(.*)/, "bar"], [/(bar)/, "foo"]]
patterns_and_values.each do |p|
    the_match = the_string.match(p[0])
    if the_match then
        return p[1]
    end
end

To make this more useful, I'd like to be able to use the subexpression
globals in the value that is returned, like so:

patterns = [[/(foo)(.*)/, $~[0]], [/(bar)/, $~[1]]

However, what is actually returned is the value of $~[0] at the time
that the patterns array was created, which is nil. Is there a good way
to achieve this without resorting to eval? I'd like to keep the syntax
of the patterns_and_values array as simple as possible, since this
will be exposed to users so that they can add to it as necessary.

Thank you kindly in advance (and apologies if the above syntax isn't
quite right - I don't have Ruby installed on this machine).

--Mike Leonard