Hi, try this,

#!/usr/bin/perl -w

use strict;
use Tk;

my $mw = 'MainWindow'->new();

#Remove the Borders
my $cv0 = $mw->Canvas( qw! -background red -highlightthickness 0!  )
             ->pack( qw! -fill both -expand 1 ! );

my $cv1 = $mw->Canvas( qw! -background blue  -highlightthickness 0! )
             ->pack( qw! -fill both -expand 1 ! );

#Change the color of the Borders
my $cv0 = $mw->Canvas( qw! -background red -highlightbackground cyan! 
+ )
             ->pack( qw! -fill both -expand 1 ! );

my $cv1 = $mw->Canvas( qw! -background blue  -highlightbackground oran
+ge! )
             ->pack( qw! -fill both -expand 1 ! );


MainLoop();
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