use Tk;
my_long_sub {
     print "You can't kill me!\n";
     sleep 60;
     my_long_sub();
            }
$main = MainWindow->new;
$main->Button( -text "Start Long Sub", -command \&my_long_sub)->pack;


##</code><code>##

use Tk;
$seconds = 60;
not_a_long_sub {
     print "You can't kill me!\n";
     #sleep 60;          <-Replacing this with an after
     #my_long_sub();     <-After handles the call
            }
$main = MainWindow->new;
$main->Button( -text "Start Long Sub", -command \&not_a_long_sub)->pack;
$main->after($seconds * 1000, \&not_a_long_sub);