1 small comment i'd like to make is on the following part: 
sub add {
    my $self   = shift;
    my @units  = @{ $self->{units} };
    my %pieces = %{ $self->{bills} };

    my $temp = shift;

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I personally use the guideline that it's best to clean out @_ and assign all the values that i need before doing anything else. 9 out of 10 times this is completely unnecessary, but consistently doing it does prevent me from leaving things in @_ only to have them changed later, yielding unpredictable results. so my advice would be to start off with my ($self, $temp) = @_; and then to proceed with the remainder of the sub.

In reply to Re: Payment changer by Forsaken
in thread Payment changer by uksza

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