From: Mark Hubbart <discordantus@...>
Date: 2005-01-18T07:51:37+09:00
Subject: Re: My regexp stupidity needs assistance before loose all my hair!

On Tue, 18 Jan 2005 07:31:06 +0900, Assaph Mehr <assaph@gmail.com> wrote:
> > I had an escape character match in the regexp:
> >
> >   / [^`] \[(.+?)\] /x
> >
> > That was messing it up (Don't really know why) but I just "zeroed"
> it:
> >
> >   / (?=[^`]) \[(.+?)\] /x
> >
> > And that did the trick.
> 
> Thats because [^`] will match 'a single character that is not `'.
> When you did the zero-width lookahead, you made into 'possibly a
> character, so long as it's not ` '.

I may be reading this wrong, but I think that with the zero-width
lookahead, it is now ensuring that the first character of the match is
not a backtick. Which, since it's always going to be a square bracket,
makes the lookahead superfluous.

If you need escaping, try:
/(?:  # escape sequence match
    ^ | [^`]  # alternate: match either "start of line" or a non-backtick.
  )
  (    # non-greedy [foo] match
    \[.*?\]
)/

... then use $1. This one won't match any paired square brackets
immediately preceded by a backtick.

cheers,
Mark