Puzzle: What is the largest integer whose digits are all different (and do not include 0) that is divisible by each of its individual digits?

tphyahoo has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I saw this puzzle mentioned at Does Visual studio Rot the Brain (linked to from slashdot today). The author solved it with c and I thought I'd give it a whack with perl. I didn't google around for solutions, on purpose, cause I wanted to do it myself.

My solution is below. It's been running for a bit, and still hasn't spit out an answer. I'm wondering if anybody out there has a faster way to do it, or if anyone would care to comment on my code.

One thought I had was, I don't really know threads but I wonder... could threads speed this up (obviously at the cost of using more computer resources).

I suspect there are other number theory tricks that could be applied here as well, but I don't know them either.

Well, Over and out monks :)

#What is the largest integer whose digits are all different (and do no
+t include 0) that is divisible by each of its individual digits?
#Requirements:
# -- Integer
# -- Digits all different (largest possible would be 987654321)
# -- Divisible by each of individual digits
# note: 
#    this integer cannot contain the digit 5 if it also contains any e
+ven digit, 
#    because then the number would be divisible by 10, and the last di
+git would be 0
#    similarly, if the last digit is odd, it can't contain any other e
+ven digit.

use strict;
use warnings;

my $max_number = 987654321;
#my $max_number = 10000;
foreach ( 0 .. $max_number - 1 ) {
    my $test_number = $max_number - $_;
    print "number / 100000: " . $test_number/100000 . "\n" if $test_nu
+mber % 100000 == 0;
    if ( passes($test_number) ) {
        print "$test_number passes!\n"; 
        die;
    }
}

sub passes {
    my $test_number = shift() || die "no test number";
    my @digits = split("", $test_number);
    my %seen;
    my $last_digit;

    #fail if see the same digit twice.
    foreach (  @digits ) {
        return 0 if $_ == 0; #fail if contains 0
        return 0 if $seen{$_};
        $seen{$_} = 1;
    }
    #set the last digit
    $last_digit = $digits[$#digits];

    #fail if contains 5, and any other digit is even
    #or the last digit is 1, and any other digit is even 
    if ( $seen{5} || $last_digit % 2 == 1 ) {
        for ( qw(2 4 6 8) ) {
            return 0 if $seen{$_}; 
        }        
    }

    for ( keys %seen ) {
        return 0 unless $test_number % $_ == 0 ;
    }
    return 1;
}
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UPDATE: Re the answers I've gotten so far, let me just say, I'm awed. Back to work...

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