#!/usr/bin/perl
use strict;
use warnings;
use Algorithm::Loops qw{NestedLoops MapCar};

my $year = $ARGV[0] || 2006;
my @digit = reverse 1..9;

my $next = NestedLoops( [ ['+', '-'], ([qw{+ - / *}, '']) x $#digit ] );
while ( my @perm = $next->() ) {
    my @expr = split m|([/*+-])|, join '', MapCar { @_ } \@perm, \@digit;
    print "@expr\n" if evaluate(@expr) == $year;
}
sub evaluate {
    my @expr = @_;
    splice @expr, 0, 3, $expr[2] * ($expr[1] eq '-' ? -1 : 1);
    for (1 .. 2) {
        my $op = $_ % 2 ? qr|([*/])| : qr|([+-])|;
        for (my $i = 1; $i < $#expr;) {
            my ($x, $y) = ($expr[$i - 1], $expr[$i + 1]);
            if ($expr[$i] =~ /$op/) {
                my $val = $1 eq '*' ? $x * $y : $1 eq '/' ? $x / $y : $1 eq '+' ? $x + $y : $x - $y;
                splice @expr, $i - 1, 3, $val;
            }
            else {$i += 2}
        }
    }
    return $expr[0];    
}