What does this do for you? Does it leak in this case?

use Tk;
use strict;
my $var = 20;

my $mw = MainWindow->new();
$mw->geometry("240x200");

my $leaking_label =
    $mw->Label( -textvariable => \$var, 
                -font => q{arial 14 bold} )->place( 
                  -x => 100, -y => +50, -anchor => q{nw} )
    ->pack;

&startloop( \$var );

MainLoop;

sub startloop {
    my ($v) = @_;
    my $iid;
    $iid = $mw->repeat( 1500, sub { autorefresh($v) } );
    return;
}

sub autorefresh {
    my ($v) = @_;

    $$v += 20;
}
[download]

HTH.