#!/usr/bin/perl -w
use strict;

my $infile = $ARGV[0];
my $act = $ARGV[1];
my $included = "n";
my $lvar ="";
my @validchars = ("A", "B", "C", "D", "E", "F", "G", "H",
 "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S",
  "T", "U", "V", "W", "X", "Y", "Z");

if ($#ARGV < 1) {
  print "Usage: $0 <file> <chars>
  Where <chars> can be -a or -c:
       -a: show all charactors. (ie, spaces, etc.)
       -c: show only regular charactors, but keep case. (ie, x is different than X.)
       -r: show only regular charactors, disregard case. (ie, t and T are the same.)\n";
  exit;
}

my $count = 0;

system("cls");   #win
system("clear"); #*nix

open INPUT, "<$infile" or die "Couldn't open '$infile' : $!";
my $input = do { local $/; <INPUT> };

my %histogram;

for my $char (split //, $input) {
  $included = "n";

  if ($act eq "-a") {
    $histogram{$char}++;
    $count++;
  } elsif ($act eq "-c") {
    foreach $lvar (@validchars){
      if ($lvar eq uc($char)) {$included = "y";}
    }
    if ($included eq "y") {
      $histogram{$char}++;
      $count++;
    }
  } elsif ($act eq "-r") {
    foreach $lvar (@validchars){
      if ($lvar eq uc($char)) {$included = "y";}
    }
    if ($included eq "y") {
      $histogram{uc($char)}++;
      $count++;
    }
  } else {
    print "Bad charactor option: '$act'.\n";
    exit;
  }
};

print "Of $count charactors:\n\n";

for (keys %histogram) {
  if ($_ eq "\n") { print "'\\n' occurred $histogram{$_} times. (".(($histogram{$_}/$count)*100)."%)\n"}
  else { print "'$_'  occurred $histogram{$_} times. (".(($histogram{$_}/$count)*100)."%)\n" }
};