Sorry, did it too quick, and didn't copy and paste the code for part 3, but I cannot update the original post... here comes it:

use threads;

use strict;
use warnings;

$| ++;

open(STDERR, ">", "error.txt");

sub parser {
    my $str = shift;
    $str =~ m/^\[(\d*),(.*?)\]$/;
    print "1 = $1\n2 = $2\n";
    my $tmp = $2;
    if ($2 ne "[]") {
        my $t = threads->create("parser",$2);
        $t->join()
    }
}

my $str = "[0,[1,[2,[3,[4,[5,[6,[7,[8,[9,[]]]]]]]]]]]";
parser $str;
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