$h = {%h} personally I never seen used this way and I'd stress the standard form to take reference as in \%h

They do different things; as the {%h} will get you a reference to a shallow copy of the hash, not just a reference to the original.

>perl -e "my %h = (1,2); my $g = {%h}; $g->{1}=3; print $h{1} . ' vs '
+ . $g->{1};"
2 vs 3
[download]

I see you've spotted that in the update tho.