use Tk;
use strict;
my $mw = MainWindow->new(-title => 'CheckBox size');
my $f = $mw->Frame->pack(-side => 'top');

my $weight = "normal";

my $fch = $f->Checkbutton(

     -text     => "Weight",

    -variable => \$weight,

)->pack(-side => 'left');

my $size = 16;
$fch->configure(-font => [ -size => $size ]);

my $fch2 = $f->Checkbutton(

     -text     => "Weight",

    -variable => \$weight,

)->pack(-side => 'left');

$size = 32;
$fch2->configure(-font => [ -size => $size ]);

MainLoop;