package MyAppMod;
use strict;
# this part I am not sure.
use AppMod;
# or do I use this line?
our @ISA=qw(AppMod);

#and then do I still say:
my $am = new AppMod;
# and
my @ch_p = change_print();

# change_print() exists in AppMod too.
sub change_print {
   my @output;
# do stuff (which calls functions and global variable from AppMod)

  return (@output);
}