8q.pl

#!/usr/bin/env perl
use strict;
use warnings;

my @board = ();

solve(0);

sub solve {
        my ($num) = @_;

        my $row;
        my $column;
        for my $row (0..7){
                for my $column (0..$num-1) {
                        if ($board[$column] == $row) {
                                goto RETRY;
                        }
                        elsif (($column - $board[$column]) == ($num - $row)){
                                goto RETRY;
                        }
                        elsif (($column + $board[$column]) == ($num + $row)){
                                goto RETRY;
                        }
                }
                $board[$num] = $row;
                if ($num == 8-1) {
                        my $column = 0;
                        for $column (0..7) {
                                printf("%d", $board[$column]);
                        }
                        print "\n";
                }
                else {
                        solve($num+1);
                }
        RETRY:
        }
}