Very slick regex, but instead of using lookaheads, why not just let backtracking work its magic? :) 

$re = qr /begin
          (?:
             (?>[^be]*)
            |(??{ $re })
            | [be]
          )*
          end/x;

[download]
Note: Abigail's will be faster, but sorry, I just couldn't resist the joke. ;)

In reply to Re: Matching nested begin/ends by jryan
in thread Matching nested begin/ends by Abigail-II

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