From: Wilson Bilkovich <wilsonb@...>
Date: 2006-12-07T07:44:22+09:00
Subject: Re: Why is this regex invalid?

On 12/6/06, Daniel Finnie <danfinnie@optonline.net> wrote:
> irb(main):002:0> regex = /([0-9]*)([^\+- ]+)(.*)/
> SyntaxError: compile error
> (irb):2: invalid regular expression: /([0-9]*)([^\+- ]+)(.*)/
>          from (irb):2
>
> irb(main):003:0> regex = /([0-9]*)([^\+ -]+)(.*)/
> => /([0-9]*)([^\+ -]+)(.*)/
>
> The only thing that it different in the 2 regexps is the placement of
> the space in the square brackets, yet the first regexp is invalid and
> the 2nd valid.
>

The hyphen in the middle expression is ambiguous, because it could
either be a range or a literal.
One way is to rearrange the order so that it comes first:
/([0-9]*)([^-+ ]+)(.*)/