BEGIN {
	package Tie::Env::Warn;
	use Carp qw(cluck);
	use Tie::Hash;
	our @ISA = 'Tie::StdHash';
	sub STORE {
		my ($self, $key, $value) = @_;
		cluck "Modification of \$ENV{$key}!";
		$self->SUPER::STORE($key, $value);
	}
	tie %ENV, __PACKAGE__;
};