First thing I noticed is that:

• you didn't specify @ISA = (Tie::Hash); (or StdHash, ExtraHash) in your toy::hash package.
• You are not supposed to call those CLEAR, DELETE etc directly, you are supposed to just use toy::hash as a usual hash.

A quick demo:

package myhash;

require Tie::Hash;
@ISA = (Tie::StdHash);

sub DELETE {
   print "in my own delete"; #it should do something more meaningful, 
+this is just a demo
}

1;

myhash.pl: (a testbed)

use myhash;

tie %a, 'myhash';
delete $a{"a"};
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