#!/usr/bin/perl

# http://perlmonks.org/?node_id=1145607

use File::Slurp;
use strict;
use warnings;

my $f1 = shift;
my $f2 = shift;

my (%hash1, %hash2);
$hash1{$_} = 1 for lc(read_file $f1) =~ /[A-Za-z0-9]+/g;
$hash2{$_} = 1 for lc(read_file $f2) =~ /[A-Za-z0-9]+/g;

my $count = my @common = sort grep $hash2{$_}, keys %hash1;
print "count: $count\n@common\n";