#!/usr/bin/perl
use strict;
use warnings;
use Storable;

my ($src, $tgt) = @ARGV;
die "Usage: $0 <src> <tgt>" if ! defined $src || ! defined $tgt;
die "The <src> and <tgt> must be same length" if length($src) != length($tgt);

my $db = retrieve('dictionary.db');
my $path = find_path($src, $tgt, $db->{length($tgt)});
print "$path\n";

sub find_path {
    my ($src, $tgt, $list, $seen, $work) = @_;
    @$work = map {key => $_ => path => "$src->$_"}, @{$list->{$src}} if ! defined $work;
    my $next = [];    
    for (@$work) {
        my ($word, $path) = @{$_}{qw/key path/};
        next if $seen->{$word}++;
        return $path if $word eq $tgt;
        push @$next, map {key => $_, path => "$path->$_"}, @{$list->{$word}};
    }
    return find_path($src, $tgt, $list, $seen, $next) if @$next;
    return 'path not found';
}