Perl vat calc

vat.pl

#! /usr/bin/perl
# works out how much VAT you've paid on a given amount
# Change the amount on the next line for the VAT rate
# Uses a while loop to allow multiple calculations
$vat = 17.5;
print "Please enter an amount paid including the VAT or 0 to quit ........ ";
$amount = <STDIN> ;
while ($amount  !=  0)
{

$Vat = ( $amount - ($amount * 100 / (100 + $vat)));

printf("You paid %.2f VAT\n", $Vat);

print "Please enter another amount paid including the VAT ";

$amount = <STDIN> ;
}