#!/usr/bin/env perl

use strict;
use warnings;

use Data::Dump;

my @src_strings = qw{A ABA ABBCCC AAABBCD BCDD CCD D};
my @re_strings = qw{A B C};
my %count;

for my $src (@src_strings) {
    for my $re (@re_strings) {
        $count{$src}{$re}++ while $src =~ /$re/g;
    }
}

dd \%count;

##</code><code>##

{
  A => { A => 1 },
  AAABBCD => { A => 3, B => 2, C => 1 },
  ABA => { A => 2, B => 1 },
  ABBCCC => { A => 1, B => 2, C => 3 },
  BCDD => { B => 1, C => 1 },
  CCD => { C => 2 },
}