#############################################################
# Generates all combinations of a given word. A word must be 
# atleast 2 characters long. This script finds usefullness in 
# solving 'jumble words' that usually appears in newspapers
#
# Copyright (C) 2007 Srivatsa Kanchi, R
# License: GPL
#
##############################################################
use strict;
use vars qw/$usage/;

$usage = <<_EOF_;
 USAGE:  perl -w AllCombs.pl <word>
 Outputs all combinations of characters in a given word 
(input a word of 2 or more characters).

_EOF_

# sub gen_allpairs: makes a recursive call to generate all the 
# combinatons of characters of a given word
sub gen_allpairs
{
    my ($i, $j, $t, @inp_lst);	

    ($i, @inp_lst) = @_;
    $j =$i;

    if( ($i+1) == $#inp_lst )
    {
        print @inp_lst, "\n";
        $t = $inp_lst[$i];
        $inp_lst[$i] = $inp_lst[$i+1];
        $inp_lst[$i+1] = $t;
        print @inp_lst, "\n";
        return;
    }

    while(1)
    {
       	gen_allpairs($i+1, @inp_lst);
        $j++;
        last if ($j > $#inp_lst);

        $t = $inp_lst[$i];
        $inp_lst[$i] = $inp_lst[$j];
        $inp_lst[$j] = $t;
    }
}

# main 
do { print $usage; exit} if($#ARGV);
do { print "Error: Input a word of 2 or more characters\n\n"; exit} 
    if(length $ARGV[0] < 2);
 
gen_allpairs(0, split //, $ARGV[0]);