Please suggest improvements

Just a quick observation: In this part of the code:

sub push_button4
 {
 sub push_button1();
 $txt->insert('end',"Opened $filename1\n");
 sub push_button2();
 $txt->insert('end',"Opened $filename2\n");
 sub push_button3();
 $txt->insert('end',"Opened $filename3\n");

...
[download]

I’m guessing you meant to call subroutines push_button1, push_button2, and push_button3, in which case you need to remove the three occurrences of sub. In its current form, the code is simply declaring that each of these subroutines is prototyped to take no arguments (which is probably wrong, and is certainly unnecessary) — but it isn’t calling (i.e., invoking) them.

Hope that helps,