which also does work fine (with strictures)

Not for me.

$ perl -v

This is perl 5, version 12, subversion 0 (v5.12.0) built for i686-linu
+x

[snip]

$ perl -Mstrict -wle'my $pkg="Foo::"; print(defined(%$pkg)?1:0)'
defined(%hash) is deprecated at -e line 1.
        (Maybe you should just omit the defined()?)
Can't use string ("Foo::") as a HASH ref while "strict refs" in use at
+ -e line 1.
[download]

Update: Oops, seems you noticed your mistake while I was posting.