Modern perl-Tk accepts a much easier form for font specification. I don't know if it needs libXft compiled in, but I now always use:

my $face = "DejaVu Sans Mono"; # Spaces and other non-ASCII chars are 
+allowed
my $desc = $mw->Label (
    -text       => "SmartCheckin",
    -font       => "{$face} 128 bold",
    -width      => 14,
    -anchor     => "w",
    -relief     => "groove",
    -background => "grey",
    )->pack;
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