On reflection, I (Zefram) am of the opinion that it's not worth the
hassle and instability to add new features to Devel::Declare at this
stage of its lifecycle. I think D:D should support its existing uses,
and gradually fade into obsolescence as the newer syntax-bending stuff
becomes available. So I'm not incorporating your patch, even though
the feature is basically sensible.
mst (Matt Trout) reckons it'd be OK to include the feature if you're
volunteering for a share in the maintenance of Devel::Declare. If you
want to go that way, ask rafl (Florian Ragwitz) for a comaint bit,
and mst for access to the canonical repository. (rafl's github is not
canonical; it's meant to be kept up to date by rafl manually.)