#!/bin/perl -w
# works out how much VAT you've paid on a given amount
# Change the amount on the next line for the required VAT rate
$vat = 17.5;
print "Please enter an amount paid including the VAT ";
$amount = <STDIN> ;
$Vat = ( $amount - ($amount * 100 / (100 + $vat)));
printf("You paid %.2f VAT\n", $Vat);