#!/usr/bin/perl
use strict;
use warnings;
use Inline C =>;

for my $file (@ARGV) {
    open(my $fh, '<', $file) or die "Unable to open '$file' for reading: $!";
    while (<$fh>) {
        my ($set) = $_ =~ /^(\w+)/;
        powerset($set, length($set));
    }
}
__END__
__C__
#include <stdio.h>
#include <stdlib.h>

void powerset (char *set, int len) {
    static char seen[67108864];
    static int init_flag = 0;
    static long val[128];
    int i, j, k, new_len;
    long bit = 0;
    char *oldset, *newset;
    if (! init_flag) {
        memset(seen, '0', sizeof(seen));
        val['a'] = 1;        val['b'] = 2;       val['c'] = 4;       val['d'] = 8;
        val['e'] = 16;       val['f'] = 32;      val['g'] = 64;      val['h'] = 128;
        val['i'] = 256;      val['j'] = 512;     val['k'] = 1024;    val['l'] = 2048;
        val['m'] = 4096;     val['n'] = 8192;    val['o'] = 16384;   val['p'] = 32768;
        val['q'] = 65536;    val['r'] = 131072;  val['s'] = 262144;  val['t'] = 524288;
        val['u'] = 1048576;  val['v'] = 2097152; val['w'] = 4194304; val['x'] = 8388608;
        val['y'] = 16777216; val['z'] = 33554432;
        init_flag = 1;
        oldset = malloc((len + 1) * sizeof(char));
        for (i = 0; i < len; ++i) { oldset[i] = set[i]; }
        oldset[len] = '\0';
    }
    else { oldset = set; }
    for (i = 0; i < len; ++i) { bit += val[ oldset[i] ]; }
    if (seen[bit] == '1') { return; }
    seen[bit] = '1';
    printf("%s\n", oldset);
    if (len == 1) { return; }
    new_len = len - 1;
    newset = malloc((len + 1) * sizeof(char));
    for (i = 0; i < len; ++i) {
        k = 0;
        for (j = 0; j < i; ++j)       { newset[k++] = oldset[j]; }
        for (j = i + 1; j < len; ++j) { newset[k++] = oldset[j]; }
        newset[k] = '\0';
        powerset(newset, new_len);
    }
    free(newset);
}