I have yet to encounter a case when would the uninitialized warning actually help. So I'd suggest using

use warnings;
no warnings 'uninitialized';
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it might be helpfull though to be able to specify the default value for the item in arrays and hashes though. In some specific cases. What would be necessary though to treat the stuff in the attribute as a block, not evaluate it to an expression. Consider this:

my @row :default([]);
# or
my @other :default(new Foo::Bar());
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You wouldn't want the default value to be the same arrayref/object, right?

The :nocirc could be handy.