If $self->{ACLS} is a hashref, then one way to correct this is to return the hashref directly and cast it into a hash in your loop declaration:

sub acls {
    my $self = shift;
    # my %acls = \$self->{ACLS} # $self->{ACLS} is a hashref
    # return %acls;
    return $self->{ACLS};
}

foreach(keys %{$mod->acls}) {
    # code in here
}
[download]

You must make sure to include the extra braces around $mod->acls or it will try to interpret %$mod before $mod->acls. Hope this helps!