On #p5p Leonard came up with working example of taking a closure. My version of it is this:

sub Foo::DESTROY { print "foo::DESTROY called\n"; }
{
    my $x = do {my $var;  bless sub {$var}, 'Foo'; };
}
__END__
foo::DESTROY called
[download]

The fact that a simple sub { "test" } isn't garbage collected is an optimization that's poorly hidden from the user. It basically means that perl doesn't have to recompile a sub. Since eval can't be cached anyway it doesn't make sense to perform that optimization there.