Re^4: Regex's, parentheses, and the mysterious ( ??{ } ) operator

[Clovis_Sangrail]

"... our = our"

Yes, I am familiar with the reflexive property of equality. (For all X, X == X.) Can you be a little less enigmatic? Are you saying I cannot use the "our" scope? When I used "my" I created an entirely separate $paren and broke the recursion, and because I have "use strict" I cannot leave the variable undeclared. Perhaps I just cannot use "use strict"?

[AnomalousMonk]

... our is our

I think Anonymonk is concerned about the second appearance of  our $re within the  (??{ our $re }) regex subexpression. Although somewhat unfamiliar, I think this is kosher because our acts as a declaration of a package variable and  $re needs to be declared or pre-declared somehow to be referenced within the regex under full strictures. The following variations work identically with strictures (note no capturing groups within $re):

>perl -wMstrict -le
"my $s = 'x(y) (a(b)) ()() q (a(b)c()(d(e(f)g))h) q';
 ;;
 our $r3;
 $r3 = qr{
   \(
     (?:
       [^()]+
       |
       (??{ $r3 })
     )*
   \)
   }xms;
 ;;
 my @p = $s =~ m{ $r3 }xmsg;
 print qq{'$_'} for @p;
 print '--------';
 ;;
 $s =~ m{ ($r3) [^()]* ($r3) }xms;
 print qq{1 '$1'   2 '$2'};
 print '--------';
"
'(y)'
'(a(b))'
'()'
'()'
'(a(b)c()(d(e(f)g))h)'
--------
1 '(y)'   2 '(a(b))'
--------

And the OPed:

our $r3 = qr{
  ...       
    (??{ our $r3 })
  ...
  }xms;