Thanks for the help. The example shown doesn't show the box on the screen, but I was able to get it to work. I need a box with a black border and filled grey. I assume I should just draw it twice and set the color differently in between:

use PostScript::Simple;

# create a new PostScript object
$p = new PostScript::Simple(papersize => "A4",
                            colour => 1,
                            eps => 0,
                            units => "pt");

# create a new page
$p->newpage;

#select black to do border
$p->setcolour("black");
$p->box(10,10,50,50);

#select a shade of grey
$p->setcolour("grey50");
$p->box( {filled => 1}, 10,10,50,50);

$p->output("file.ps");
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