perl - How to use foreach with a hash reference?

Question

I have this code

foreach my $key (keys %ad_grp) {

    # Do something
}

which works.

How would the same look like, if I don't have %ad_grp, but a reference, $ad_grp_ref, to the hash?

Answer 1

foreach my $key (keys %$ad_grp_ref) {
    ...
}

Perl::Critic and daxim recommend the style

foreach my $key (keys %{ $ad_grp_ref }) {
    ...
}

out of concerns for readability and maintenance (so that you don't need to think hard about what to change when you need to use %{ $ad_grp_obj[3]->get_ref() } instead of %{ $ad_grp_ref })