my (%history, $histcount); 	# Should I initialise $histcount = 0 or is that "Cargo cult"?

sub addHist { 
	my ($hashref, $histcount, $new ) = @_;  # Naming our parameters makes things clearer
	# validate
	$hashref->{ $new } = $histcount++; 
}

sub getHist { 
	my ($hashref, $histcount, $new ) = @_;
	#validate
	return = grep{ $hashref->{ $_ } == ($histcount - $n); } keys %history; 
}