#!/usr/bin/perl -w
use strict;
$|++;

my %source;

# process file
while (<DATA>) {
  my ($source, $action, $sub_action) = split;
  my $source_action = $source . "||" . $action;
  # sub_action isn't required to appear

  $source{ $source }{ count }++;
  $source{ $source }{ $action }{ count }++;
  $source{ $source }{ $action }{ $sub_action }{ count }++ if $sub_action;
}

use Data::Dumper;
print Dumper \%source;

__DATA__
source1 QUEUED
source1 QUEUED
source1 CLICK linkid1
source1 CLICK linkid1
source1 CLICK linkid2
source2 QUEUED
source2 CLICK linkid1
source2 CLICK linkid1
source2 CLICK linkid2