$total = 0;
$weekCounter = 0;

print "Enter sales for week or enter quit: ";  
chomp( $sales = <STDIN> );

until ( $sales eq 'quit' ) {            
   $weekCounter++;
   $total += $sales;
   print "Enter sales for week or enter quit: ";     
   chomp( $sales = <STDIN> );
}

if ( $weekCounter != 0 ) {
   $average = $total / $weekCounter;
   print "\nSales averaged $average computers per week.\n";
}
else {
   print "\nNo sales figures were entered.\n";
}