Oops, it's been more than a week. Here's the promised code

use strict;
use warnings;

sub crack {
   my $hint   = shift;
   my $target = shift;
   my $salt   = substr($target, 0, 2);
   my @chars  = @_;
   my $base   = @chars;
   my $passwd;

   use integer;

   for (my $num_chars=0; ; $num_chars++) {
      for (my $enc=0; ; $enc++) {
         my $i = $enc;
         my $pad = '';
         for (1..$num_chars) {
            my $idx = $i % $base;
            $i = $i / $base;
            $pad .= $chars[$idx];
         }

         # Go add a character.
         last if $i;

        #$pad = reverse $pad;

         for my $pos (0..$num_chars) {
            $passwd = $pad;
            substr($passwd, $pos, 0, $hint);

            return $passwd
               if crypt($passwd, $salt) eq $target;
         }
      }
   }
}

my @chars = ('a'..'z', 'A'..'Z', '0'..'9');

print crack('12',   crypt('d12e',    'AA'), @chars), "\n";
print crack('1234', crypt('aa12345', 'AA'), @chars), "\n";
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