送られてきた値が期待した値かどうかを調べる方法の一例。
my $posted = 'values';
$sanitized = { map { $_=>$_ } qw(list of expected values) }->{$posted};
print $sanitized; #prints "values";
my $posted = 'polluted';
$sanitized = { map { $_=>$_ } qw(list of expected values) }->{$posted};
print $sanitized; #contains undef
