my $mw = new MainWindow(-title => 'Calc', -bg => 'blue');
$mw->geometry("300x300");
my $topframe = $mw->Frame(-height => '60', -width => '300', -bg => 'bl
+ack');
my $btmframe = $mw->Frame(-height => '225', -width => '300', -bg => 'r
+ed');


my $display   =  $topframe->Entry(-justify      => 'right',
                                  -state        => 'disabled', 
                                  -textvariable => \$calc)
                           ->pack(-expand       => '1',
                                  -fill         => 'x',
                                  -pady         => 30,
                                  -padx         => 20,
                                  -side         => 'right');

$mw->bind("<KeyRelease>" , sub { &keypress } );


for my $i (
qw/
   7 8 9
   4 5 6 
   1 2 3
   0 . C / )
{
$button{$i} = $btmframe->Button(-text    => "$i", 
                                -width   => '3', 
                                -height  => '1', 
                                -command => sub { &btnpress($i) })
                         ->grid(-row     => $row,
                                -column  => $column,
                                -padx    => 2, 
                                -pady    => 2,
                                -sticky  => 'nsew',
                                -ipadx   => 10, 
                                -ipady   => 10);

$column++;
if($column > 2){$column = 0; $row++;}
}




$topframe->pack(-side => 'top', -expand => '0', -fill => 'x'); 
$btmframe->pack(-side => 'top', -expand => '1', -fill => 'both'); 
MainLoop;
[download]

I would do it like so (ie, not use grid )



#!/perl/bin/perl -w

use strict;
use Tk;
use Tk::Button;
use Tk::Entry;

my $row = 0;
my $column = 0;
my $calc = "0.00";
my $buffer;
my %button;

my $mw = new MainWindow(-title => 'Calc', -bg => 'blue');
$mw->geometry("300x300");
my $topframe = $mw->Frame(-height => '40', -width => '300', -bg => 'bl
+ack');

$topframe->pack(-side => 'top', -expand => '0', -fill => 'x', -anchor,
+ 'nw'); 

my @rows;

push @rows, $mw->Frame()->pack( -expand, 1, -fill, 'both', -side, 'top
+', -padx, 3, -pady,3) for (0..3);


my $display   =  $topframe->Entry(-justify      => 'right',
                                  -state        => 'disabled', 
                                  -textvariable => \$calc)
                           ->pack(-expand       => '1',
                  -pady        => '20',
                  -padx        => '30',
                                  -fill         => 'x',
                                  -side         => 'left');

$mw->bind("<KeyRelease>" , sub { &keypress } );


my $r =0;
my $w = 0;

for my $i (
qw/
   7 8 9
   4 5 6 
   1 2 3
   0 . C / )
{



$button{$i} = $rows[$r] ->Button(-text    => "$i", 
                                -width   => '3', 
                                -height  => '1', 
                                -command => sub { &btnpress($i) })
                         ->pack( -expand, 1, -fill, 'both', -side, 'le
+ft', -padx, 2);
$w++;
if( $w == 3){ $r++; $w= 0; }

}





MainLoop;



sub btnpress{
    my $num = shift;
    if($num ne "C"){
    $buffer .= $num;
    $calc = sprintf "%0.2f", $buffer;
    }

   if($num eq "C"){  $calc = "0.00"; $buffer = 0.00; }
}

sub keypress{

    my $widget = shift;
    my $e = $widget->XEvent;    # get event object
    my $key = $e->K;
       $key=~s/period/\./ig;

    if( $key =~/c/ig ){ $key = uc $key;  $button{$key}->invoke; }
    
    if( $key =~/(\d)|\./){ &numpress($key); }

}
[download]



JamesNC