Zaxo,
Reflect that that attribute is more than a tag that you may query at runtime like some kind of metadata. I'm not sure how I'd go about querying that.
Really. I haven't found a single example of how one might modify the behavior of a subroutine using attributes outside the few built-ins. As far as querying the attributes - it was in the synopsis of perldoc attributes
use attributes (); # optional, to get subroutine declarations
my @attrlist = attributes::get(\&foo);
I have looked at
Attribute::Handlers and still felt unsatisfied.
Attribute::Handlers::Prospective looks promising after glancing at the documentation but I find it hard to believe that there are no code examples outside the module. Why is this I wonder. It seems to me that you are right - the majority of us are in the dark and so attributes, if useful at all as others have implied, are way underdeveloped in perl.