gtk2 is a c-library -?
Here is an example in cpp pseudo code how I understood coding with tvision:

class button { // The tvision class
public:
virtual void buttonclick(){
//Overwrite me ...
}
...
}

class mybutton public Button { // This is my button
...
virtual void buttonclick(){
  //do something
  exit(0);
}
}

int main(){
//Initialize the app..
app->mainloop();
}
[download]

TVision is object oriented, and I don't know howto implement the example of the class mybutton in perl in a useful manner.

I thought already about a wrapper which implements event style hooks.

Would look something like this:

--- cpp layer
class perlwrapper_button public Button{
virtual void buttonclick(){
   if ( !call perl->this_instance->buttonclick() ){
      Button::buttonclick(); // Call tvision's buttononclick
  }
}
}
--- perl module
package Button;
sub buttonclick{
  return 0;
}
1;

--- The perl code of mybutton:
package MyButton;
push @ISA, 'Button';

sub buttonclick{
  exit(0);
}
1;
[download]

I doubt, however, this concept is wise.