Basic Perl Scripting
Exercise 6
To be handed in (per email to kathrin@theochem.kth.se): Friday, October 26th

In this exercise you should write an interactive script for selling
Perl books. You can have a look at page 32 which gives an equvivalent
example selling tickets. We assume you have 500 Programming Perl books
to sell, each costing 40 euro. Your script should do the following: On
the standard input (<STDIN>) it should ask the customer for their name
and how many copies he/she wants to buy. When he/she gives the number,
the script should calculate the price and return that value. The
customer should then be given the option to say Yes or No to the
purchase. If the customer agrees to buy a certain number of books,
this number should be substracted from the available number of books
(so you do not end up selling more than 500 copies). Remember to
account for unexpetced answers also (for example, if the customer does
not specify a number, the script has to return an error message to him
like "Please specify a number").

The in and output could look similar to this:
----------------------------------
Hello, who am I talking too?
Anna

Hello, Anna. We have 500 Programming Perl books available, each
costing 40 euro. How many would you like to purchase?

50

The price for 50 books is going to be 2000 Euro. Would you like to
proceed, yes or no?

yes

Thank you, Anna, for your purchase of 50 Programming Perl books.

----------------------------------

Hand in your script and the output.