use strict;
use warnings;

use Tk;

my $tstate = 0;    # State of the dynamic text

my $mw = MainWindow->new(                          # Create a window
      -width      => 300,
      -height     => 110,
);
$mw->minsize( 300, 110 );

$mw->fontCreate('standard_font',                   # ..and some fonts for it 
                 -family => 'Arial', -size => 12, 
                 -weight => 'normal');

$mw->fontCreate('alternate_font', 
                 -family => 'Times', -size => 24, 
                 -weight => 'bold');

$mw->fontCreate('my_default_font', 
                 -family => 'Sans', -size => 8, 
                 -weight => 'normal');
                 
# $mw->configure(-font => 'my_default_font');        # '-font' is unknown to configure()
# $mw->fontConfigure('my_default_font');             # Does nothing

my $static_text_lbl = $mw->Label(                  # Uses the system 'default' font
      -text => 'UNCHANGING TEXT',
   )->pack(-anchor => "center", -side => 'top');
   
my $text_lbl = $mw->Label(                         # An object with an assigned font
      -text => 'DYNAMIC TEXT',
      -font => 'standard_font',
   )->pack(-anchor => "n", -side => 'top');
              
my $Exit_Btn = $mw->Button(                        # A button to exit
      -text => 'Exit',
      -width => 8,
      -command => sub { $mw->destroy },
)->pack(-anchor => 's', -side => 'bottom');

my $Toggle_Btn = $mw->Button(                      # ..and another to toggle the font
      -text => 'Toggle',
      -command => [ \&fix_fonts ],
)->pack(-anchor => 's', -side => 'bottom');

MainLoop;

# ----------

sub fix_fonts
{
   if ($tstate ^= 1) {
      $text_lbl->configure(-font => 'alternate_font')
   
   } else {
      $text_lbl->configure(-font => 'standard_font')
   
   }

}

# [eof]