One thing I have discovered recently about Tk fonts, is for the most part, you can forget passing the whole font-family string, Tk will happily just take the size. For instance, look at this extremely simple example.

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

my $size = 12;
my $main = new MainWindow();
$main->geometry('400x400+200+200');

my $font = $main->fontCreate(
          -size => $size,
          -weight => 'bold');

my $button;
$button = $main->Button(-text => "+",
           -font => $font,
           -command =>    sub{
                    $button->configure( -font=> $main->fontCreate(
                           -size => $size++,
                          -weight => 'bold')),
                      } );

$button->pack();

MainLoop;
[download]

++mikepol for asking
++zentara for his answer (and all his much appreciated pTk expertise over the years)

I know this is an old thread, but just had a similar question and could not find a suitable answer anywhere (on-site or off-site).

After banging my head against things for long enough, I came up with this solution. Hopefully, it will help others in the future.

-Craig

use strict;
use warnings;

use Tk;
use Tk::Text;
use Tk::Font;

use Data::Dumper;

# Create pTk text window...
my $mw = MainWindow->new(-title => 'Text Font');
my $txt = $mw->Scrolled('Text')->pack(-fill => 'x', -side => 'left');

# Get Current font...
my $currfont = $txt->cget(-font);

# Create new font by cloning & modifying current font...
my $boldfont= $currfont->Clone(-weight=>'bold');

# configure new tag ('bold') causing tagged characters to use the new 
+bold font...
$txt->tagConfigure('bold', -font => $boldfont);

# Insert some text that is not tagged as bold...
$txt->insert('end', "========================\n");
$txt->insert('end', "Default font requested:\n" . Dumper($currfont));
$txt->insert('end', "\nDefault font chosen:\n" . Dumper($currfont->act
+ual));

# Insert some text that is tagged as bold...
$txt->insert('end', "========================\n");
$txt->insert('end', "Bold font requested:\n" . Dumper($boldfont), ['bo
+ld']);
$txt->insert('end', "\nBold font chosen:\n" . Dumper($boldfont->actual
+), ['bold']);

MainLoop;
[download]