#!/usr/bin/env perl
#
# isograms - prints the isograms in the input
#
# $Id: isograms 711 2010-03-05 23:21:52Z rp $

# An isogram is a word in which every character occurs equally often;
# this script takes a word to be a maximal sequence of ASCII alphabet chars.

use warnings;
use strict;

use Getopt::Std;

my %opt; getopts('hi', \%opt);

&help if $opt{h};

sub help
{
  print <<ZZ;

Usage: $0 [-i] [file1 [file2 [...]]]

to print all maximal sequences of ASCII alphabet characters
in the input for which it holds that no character occurs twice.

Option:

  -i  compare case-insensitively

ZZ

 exit(0);
}

my $cily = $opt{i};

my %wc;

while (<>)
{
  foreach my $w (/[a-z]+/ig)
  {
    my $w2match = $cily ? lc($w) : $w;

    next if $wc{$w2match}++;

    my %cc;

    foreach my $c (split(//, $w2match))
    {
      ++$cc{$c};
    }

    my ($c1, @cs) = values %cc;

    if (!grep { $_ != $c1 } @cs)
    {
      print $w, $/;
    }
  }
}