Here is some code that starts off IE as a separate process, then sleeps - in your case, you would run your TK code.

THe parent program will not terminate until the TK code finishes AND IE is closed.

# Start child process
defined(my $pid = fork) or die qq(Can't fork: $!\n);

if ($pid==0){
  #Child process
  print qq(In Child .. starting \n); 
  # Start IE
  system '%ProgramFiles%/internet explorer/iexplore.exe','http://cnn.c
+om';
  print qq(child returns - child quitting\n);
  exit 0
};
# THis is the parent Process .. do TK stuff here..
 print qq(PARENT:$pid doing...\n);
 sleep 5;
 print qq(Parent done\n);
 ## Code will HANG here until Iexplorer is closed....
[download]

Tested on Windows XP with perl, v5.8.0 built for MSWin32-x86-multi-thread.