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

my @array_1 = qw/A B/;
my @array_2 = qw/A B C D A D B A C/;

my %check_1 = map { $_ => 1 } @array_1;
my %counts;
map { $counts{$_}++ if $check_1{$_} } @array_2;

print "$_ : $counts{$_}\n" for keys %counts;