#!/usr/bin/perl -w
#-*-cperl-*-

use strict;

=pod

puzzle.pl - print a list of five letter words for a puzzle answer

usage:

       puzzle.pl [dictionary_file]

This script addresses the 12 August 2001 puzzle from Weekend Edition
Sunday puzzle ( http://www.npr.org/programs/wesun/puzzle/ )

Name a well-known international food in five letters. Move the first
two letters to the end. The result will be another well-known 
international food in five letters. What foods are these? They are
both foods that originated overseas, but are now popular in the
United States and around the world.

We cycle through a dictionary file, either one provided on the
command line or the standard dictionary ( /usr/share/dict/words
on many *nix ).  We find words that fit the above criteria and print
them out.

You'll have to do the definition legwork, unless you want to write
some tool to do that, too.

=cut

my $dictionary = $ARGV[0] || "/usr/share/dict/words";
open ( DICT, "< $dictionary" )
  or die "Cannot open $dictionary: $!\n";

my %fives;

foreach ( <DICT> ) {               # go through the dictionary
  chomp;                           # strip the /n
  $fives{$_} = undef               # slap them into a hash
    if ( length $_ == 5 );         # we only want 5 letter words
}

close DICT;

foreach my $word ( keys %fives ) { # cycle thru the 5 letter words
  $_ = pack (                        # put it back together
	     "A3 A2", (                 # back-end first
		       unpack (            # split it, moving ahead 2
			       "x2 A3 X5 A2", # take 3, go back 5
			       $word            # and take 2
			      )
		      )
	    );
  print $word , "\t" , $_ , "\n"   # print the result & orig. word
    if ( exists $fives{$_} );      # if the result is a real word
}