#!/usr/bin/perl
use strict;
use warnings;
my %charCount;
my $corpus = join('', <DATA>);

$corpus =~ tr/A-Z/a-z/d; # Map uppercase to lowercase
$corpus =~ tr/a-z//cd;   # Delete all but lowercase

$charCount{$_}++ for split //, $corpus;

for (sort keys %charCount) {
    print "$_ : $charCount{$_}\n";
}

__DATA__
Now is the time for all good men to come to the aid of their party.
The quick red fox jumped over the lazy brown dog.
The warrior swings the +6 axe at the orcs standing in front of him.