use Tcl::Tk qw(:perlTk);
my $int = new Tcl::Tk;
$int->Eval(<<'EOS');
#...you...paste...tcl/tk code here
# or write it
source /path/to/my/file
EOS

# here you can access Tcl/Tk widgets by using
my $button = $int->widget(".ff.path.to.widget");
# and tie perl variable to Tcl variable and it is
# configured to be displayed on GUI
my $labtext;
tie $labtext, 'Tcl::Var', $int, "labtext";

# for example
$button->configure( -command=> sub {
  print "Hey, man, you just pressed the button\n";
  $labtext = "indeed, that man pressed the button";
});

$int->MainLoop;