1- isa/can validation in XS allows this:
2
3 { a => { isa => \%hash } }
4
5and tries to see if a->isa("HASH(0x1581)").  Instead, we should die if
6given a non-array reference.  Same for can, etc.  See how this is
7handled in callbacks for example.
8
9
10- make it possible to explicitly not use the XS version in a non-hacky
11way.
12
13
14- is there something better than "N/A" that could be used when
15validation is being done outside a sub?
16
17
18- add an excludes param to the spec as the opposite of depends,
19suggested by Diab Jerius (see rt.cpan.org).
20