The thing that is powerful, and a bit tricky to master, is the concept of tags. You can devise very intricate schemes with tags and hashes of objects. Here is the basic idea. The number is centered here, but I tagged it upper-left-corner, to show you that you can create multiple text objects in the rectangles and refer to them differently with tags, and raise. lower, configure to be hidden, etc.

Your problem will be to find a way to reference the text creation points with respect to the location of the various rectangles on the canvas. It can all be done, maybe using 'groups' or make them independent objects, and do something like "my $cell{1}{'obj} = new Cell(-x=>$x,-y=>$y) in some sort of double loop to make your grid. Then all your need to do is make text points in the object, (or even a plain hash will do), and you can get them with syntax like $cell{2}{upper_left}, etc. Or if OO, $cell{2}->upper_left

#!/usr/bin/perl
use Tk;
use strict;
my $w=20;
my $x=0;
my $y=0;

my %nums = (
   0 => ['black','yellow'],
   1 => ['yellow','black'],
   2 => ['white','green'],
   3 => ['green','white'],
   4 => ['grey','red'],
   5 => ['red','grey'],
   6 => ['blue','white'],
   7 => ['white','blue'],
   8 => ['orange','grey45'],
   9 => ['grey45','orange'],
);


my $mw=tkinit;
my $c = $mw->Canvas->pack;

for (0..9) {
 my $item=$c->createRectangle($x,$y,$x+20,$y+20,
             -fill=> ${$nums{$_}}[0],
             -tags => ['rect']
          );

my $text = $c->createText($x+10,$y+10,
           -anchor=>'center',
           -fill => ${$nums{$_}}[1],
           -text => $_,
           -tags => ['num','upper-left-corner']
          );

      $x+=20;
}

$mw->Button(
    -text    => "Hide Text",
    -command => sub {
            $c->lower('num','rect');
             })->pack;

$mw->Button(
    -text    => "Show Text",
    -command => sub {
            $c->raise('num','rect');
             })->pack;
MainLoop;
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