Question

I have been looking for a way to match balanced parenthesis in a regex and found a way in Perl, that uses a recursive regular expression:

my $re;
$re = qr{
           \(
              (?:
                 (?> [^()]+ )       # Non-parens without backtracking
                 |
                 (??{ $re })        # Group with matching parens
              )*
           \)
         }x;

from the perl regular expression site
.

Is there a way to do this in Ruby or a similar language?

UPDATE:

For those interested here are some interesting links:

Oniguruma manual – from Sawa’s answer.

Pragmatic Programmers’ Ruby 1.9 Regular Expressions Sample Chapter

Answer 1

Yes. With oniguruma regex engine, which is built in in Ruby 1.9, and is installable on Ruby 1.8, you can do that. You name a subregex with (?<name>...) or (?'name'...). Then you call a subregex with \g<name> or \g'name' within the same regex. So your regex translated to oniguruma regex will be:

re = %r{
  (?<re>
    \(
      (?:
        (?> [^()]+ )
        |
        \g<re>
      )*
    \)
  )
}x

Also note that multi-byte string module in PHP >=5 uses oniguruma regex engine, so you will be able to do the same.

The manual for oniguruma is here.