my $_cardCharged = chargeCard($_billingInfo);

sub chargeCard {
	%_billingInfo = shift;

# AND

	my $_cardCharged = chargeCard(\$_billingInfo);

sub chargeCard {
	%_billingInfo = shift;

# AND
	my $_cardCharged = chargeCard(%_billingInfo);

sub chargeCard {
	%_billingInfo = shift;

# AND

	my $_cardCharged = chargeCard(\%_billingInfo);

sub chargeCard {
	%_billingInfo = shift;

# AND every other way I can think of...