#!/usr/bin/perl
use CGI;
my $q = new CGI;
my $summ = 100;
my $peritem = 1;
print "Content-type: text/html\n\n";
unless ($q->param('buyit')) {
print "You have $summ coins.
All items cost $peritem coin.";
} else {
my $num = int($q->param('items'));
my $cost = sprintf("%.2f", $num * $peritem);
print "You try to buy $num items, for $cost coins.
";
if ($cost > $summ) {
print "You have not enough money
";
} elsif ($cost < 0) {
print "Invalid number
";
} else {
$summ-=$cost;
print "You buy $num items for $cost coins. You have $summ coins left
";
}
}