I can of course work with this limitation, but it's not completely satisfying since it was not necessary before (don't remember version of perl, 5+years ago)

That's not true. Variable declarations have always taken effect in the statement following the one containing the declaration. Perhaps you weren't using lexical ("my") variables (or strict) "5+ years ago".

Unrelated, don't use lexicals from outside the pattern inside of (?{ ... }), (??{ ... }) and anything similar. 

$ perl -wE'
   sub f {
      my $x = $_[0];
      "" =~ /(??{ say $x; "" })/;
   }
   f("abc");
   f("def");
'
Variable "$x" will not stay shared at (re_eval 1) line 1.
abc
abc

[download]

Use a package variable instead. 

$ perl -wE'
   sub f {
      local our $x = $_[0];
      "" =~ /(??{ say $x; "" })/;
   }
   f("abc");
   f("def");
'
abc
def

[download]

In reply to Re: (??{ code }) versus (?PARNO) for recursive regular expressions by ikegami
in thread (??{ code }) versus (?PARNO) for recursive regular expressions by wind

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