Your regex is only being compiled once, and in this compilation, it makes note of the variable you're using. Thus, it creates an "accidental" closure. Here is my proof: 
### update: fixed
### thanks Hof -- I condensed working code poorly :(

use re 'eval';

my @r;
my $p = q/.(?{ ++$x[0] })^/;
for (0..2) {
  my @x = (0);
  "ab" =~ $p;
  push @r, \@x;
}
print "$_->[0]" for @r;

[download]
That code prints 600. If, however, you cause the regex to change, such that it requires recompilation, the binding to the previous @x is gone, and the new @x is bound.

If you were to use qr// instead, you'd be changing the global array.

You're doing some funny-looking scope-crufting. I'd stay away from it if I were you. This situation is the sort of thing I fear having to write about and explain in my book.

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker.
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

In reply to Re: Perl Bug in Regex Code Block? by japhy
in thread Perl Bug in Regex Code Block? by Hofmator

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