Tk and O-O

Tk is a Perl package for building graphical user interfaces.

Originally written for the low-level functionality of Unix X Windows.
A fellow Perl programmer added a generic porting layer and a Perl wrapper in the object-oriented module Tk.pm

O-O Review

An object is a predefined data structure.
Methods are subroutines that operate on this data.
Invoke them with the -> arrow notation.
- Class methods are ordinary subroutines.
- They do not operate on a particular instance of the object.
  $obj = Package::new();
  $top = MainWindow->new();
  or
  $top = new MainWindow
- Instance methods operate on a particular instance of the object.
  $label = $top->Label(text => 'hello world!');