my $len = 6;
my $hint = q(1234);
my $free = $len - length $hint;
my @brute_list;

for my $seed ( '0'x$free .. '9'x$free ) {
    for ( 0 .. $free ) {
        my $string = $seed;
        substr( $string, $_, 0) = $hint;
        push @brute_list, $string;
    }
}

print "@{brute_list}$/";