#!/usr/bin/perl
use strict;
use warnings;
my $n =($ARGV[0] || 8);
# usage : perl queens.pl n
# ex : perl queens.pl 20
#############

use re 'eval';

my $p=1;
my @s;
local our @r;  
my $str;
my $re='_(\d+)!';
for my $i (1..$n) {
    for my $j (1..$n) {
        $str.= join '!',"_$j",(map {join';',$j-$_<0?0:$j-$_,$j+$_ >$n?0:$j+$_} (1..($n-$i))),'';
    }
    $str.="\n";
    push @s,$p+1,$p+2;
    push @r,$p;
    $re.=($i==$n)?'':(('(\d+);(\d+)!'x($n-$i)).".*?\n.*?_(?!(?:\\".(join '|\\',@r,@s).')!)(\d+)!');
    $p+=2*($n-$i)+1;
    $_+=2 for @s;
}

$re .=
'(?{
   my $l = "a";
   print join",",map{$l++.eval"\$$_"}@r;
   print "\n";
})(?!)';

$str=~$re;