Ah, specifically, the "Back reference with nest level" section of
http://oniguruma.rubyforge.org/oniguruma/files/Syntax_txt.html

On Jan 23, 2009, at 7:14 PM, Rob Biedenharn wrote:

> I think that you need to look at what Oniguruma might be able to do.
> http://oniguruma.rubyforge.org/
>
> I believe I've seen it demonstrated that balanced open/close pairs
> can be found with this regular expression engine. It might be ugly,
> however, but then you probably expected that.
>
> -Rob
>
> On Jan 23, 2009, at 5:33 PM, ivo welch wrote:
>
>> Dear Experts:  I am very new to ruby, literally having just read the
>> ruby book.
>>
>> I want to write a program that does basic LaTeX parsing, so I need to
>> match '}' closings to the opening '{'.  (yes, I understand that LaTeX
>> has very messy syntax, so this will only work for certain LaTeX
>> docs.)
>> Does a gem exist that facilitates closing-paren-matching fairly
>> painlessly?  For example,
>>
>> sample = " \caption{my table \label{table-label} example:
>> $\sqrt{2+\sqrt{2}}$} more here {}"
>>
>> so, I want to find my "\caption" matcher ruby program to be able to
>> detect the closing paren, and provide me with everything in between
>> the opener and closer (i.e., "my table \label{table-label} example:
>> $\sqrt{2+\sqrt{2}}$").  Possible?
>>
>> I searched this mailing list first, but I only found discussions from
>> years back about this issue.  I understand that this is not strictly
>> speaking a regular expression.  I come from a perl background.  There
>> are now some regex extension libraries that make it possible for the
>> built-in regex engine to parse matching parens
>> (Regexp::Common::balanced and Text::Balanced).  I was hoping I could
>> find some similar gem for ruby.
>>
>> help appreciated.
>>
>> Sincerely,
>>
>> /iaw
>>
>
>