sub get_data {
  # returns scalar data pointer to my structure
  my $return_value;
  my $db = open_database($credentials); # must declare this above
  my $data = query_db($db, "select * from bar");
  $return_value = massage_data($data);
  return $return_value;
}

sub open_database {
  my $cred = shift;
  warn "open_database doing nothing";
  return undef;
}
...