sub strip_US_CA_dup_hols {
	for my $country (@cntry_of_issue) {
		for my $holiday (@{$countries{$country}}) {
			$seen{$holiday}++;
		}
	}
	for my $country (@cntry_of_issue) {
        my $aref = $countries{$country};
        @$aref = grep { $seen{$_} < 2 } @$aref;
    }
}

# Prints:

'US' => [
		'20120116',
		'20120528',
		'20120704',
		'20121122'
	  ],
'CA' => [
		'20120521',
		'20120702',
		'20120806',
		'20121008',
		'20121226'
	  ]