Add a value to the -variable option
The following example sets "red4" as the default value even though "Black" is first in the array list.
use Tk;
my $mw = MainWindow->new;
my $palette = 'red4';
my @colors = qw/Black red4 DarkGreen NavyBlue gray75 Red Green Blue
gray50 Yellow Cyan Magenta White Brown DarkSeaGreen DarkViolet/;
my $om = $mw->Optionmenu(
-variable => \$palette,
-options => [@colors],
-command => [sub {print "args=@_.\n"}, 'First'],
);
$om->pack;
MainLoop;