use warnings;
use strict;

my @digits_used;
#$digits_used = [false x 10];
find_digits(1, 0);  #// get the ball rolling

sub find_digits {
    my ($depth, $total) = @_;
    for my $digit (0..9) {
        if( not $digits_used[$digit]) {
            $digits_used[$digit] = 1;
            if ($depth < 4) {
                find_digits($depth+1, ($total+$digit)*10);   #// recurse
            } else {
                print $total+$digit,"\n";
            }
            $digits_used[$digit] = 0;
        } #// if used
    } #// for digits
} #// end sub

__END__

c:\usr\scripts>sundial.pl | find /c /v ""
5040