Thanks everyone for these numerous approaches!

As it seems the our approach is not that bad. Nevertheless, the more CGI::Application-way of doing it seems to be to declare my %hash and then stuff a ref to it into $self->param('hashref'); consequently pulling the ref/the hash into scope at the entry of each runmode subroutine with my $hashref = $self->param('hashref');

I will see if I will migrate away from the current global approach. Further hacking on my script may lead there.. Again, thanks everyone!