You could make your first file -- the one with code you "want to append" -- simply call the functions from the second file, then run some code afterwards. Presumably you have a third file calling the functions in question, so you would change that to use the first file instead of the second.

Maybe some example code will make more sense:

# File1.pm
package File1;
use File2;

sub foo {
  File2::foo(@_);
  other();
  code();
  appended();
  here();
}

1;

# File2.pm
package File2;

sub foo {
  original();
  code();
  here();
}

1;

# File 3
use File1;
File1::foo(); # this will call File2::foo() behind the scenes
[download]

I have to wonder why you want to do this, though. It sounds like a sort of fishy request. Perhaps it would be a good idea to look into OO and use inheritance. Perhaps not. Without any details, we can't really give any good suggestions.