Thank you for the sanity check. I ran your above statements on strawberry perl v5.12.1

> perl -e"use strict; our $x = $x;"
> perl -e"use strict; our $x = qr/(??{ $x })/;"
Variable "$x" is not imported at (re_eval 1) line 2.
Global symbol "$x" requires explicit package name at (re_eval 1) line 
+2.
Compilation failed in regexp at -e line 1.
> perl -e"use strict; my $x = qr/(??{ $x })/;"
Global symbol "$x" requires explicit package name at (re_eval 1) line 
+2.
Compilation failed in regexp at -e line 1.
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And on perl v5.10.0 built for i686-linux

$ perl -e'use strict; our $x=$x;'
$ perl -e'use strict; our $x=qr/(??{ $x })/;'
Variable "$x" is not imported at (re_eval 1) line 2.
Global symbol "$x" requires explicit package name at (re_eval 1) line 
+2.
Compilation failed in regexp at -e line 1.
$ perl -e'use strict; my $x = qr/(??{ $x })/;'
Global symbol "$x" requires explicit package name at (re_eval 1) line 
+2.
Compilation failed in regexp at -e line 1.
[download]

However, done on perl v5.8.0 built for i386-linux-thread-multi, I get no strictures errors and the original parsing code works as desired.:

$ perl -e'use strict; our $x = $x'
$ perl -e'use strict; our $x = qr/(??{ $x })/;'
$ perl -e'use strict; my $x = qr/(??{ $x })/;'
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So this change to the way (??{ code }) was validated for strictures changed at least after v5.8.0. Maybe this was done when (?PARNO) was introduced in v5.10.0. I guess that's one way to encourage people to move to a new feature. Gotta say it's still annoying though.

Update: Added data on my declarations using (??{ code }) per ikegami's request.

Try

perl -e'use strict; my $x = qr/(??{ $x })/;'
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on 5.8.0 for me please

I've added the requested information to the previous reply. However, to be thorough, I've run the full script on v5.8.0 as well. When using our $x = qr/(??{ $x })/;, the script works as desired. However, when using my $x = qr/(??{ $x })/;, the script throws no strictures errors, but does throw a warning:

$ perl rec_regex.pl
Use of uninitialized value in substitution iterator at perm.pl line 17
+, <DATA> line 1.
<7> { ... } </7>
<7> { { } } </7>
{ <7> { { } } </7> }
{ <3> { } </3> { <7> { { } } </7> } }
<7> { ... } </7>
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Additionally, as you can see it only does the second level of recursion again. Nevertheless, I never used my originally, so just sharing for addition data.

Also note, I just discovered that the original code DOES work currently if declared with our. It just won't pass strictures validation. Will update my original question with this data soon as I get back from pharmacy. Got a toothache coming on.