I found that font specifications are tricky to get working, unless you use the following methods.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = new MainWindow;

$mw->fontCreate('big',
   -family=>'arial',
  -weight=>'bold',
  -size=>int(-18*18/14));

$mw->fontCreate('medium',
   -family=>'courier',
   -weight=>'bold',
   -size=>int(-14*14/10));


my $entry = $mw->Entry(-font =>'big',-text=>'Big')->pack();
my $entry1 = $mw->Entry(-font =>'medium',-text=>'medium')->pack();

MainLoop;
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