So, I code the following to set the properties to 5 millimeters.:

funny, where do you get that from?

 Wx::Point->new( x, y );

my wxWidgets / wxPerl / wxGlade tutorial, http://www.wxperl.it/p/wxperl-primer.html

A fleshed out working example would be GREATLY appreciated.

:) I've no interest starting from scratch

use Wx qw' :allclasses ';
my $psdd = Wx::PageSetupDialogData->new;

my $p = $psdd ->GetMarginBottomRight;
print $p->y, ' ', $p->x, "\n";

$psdd->SetMarginBottomRight([6,6]); 

$p = $psdd ->GetMarginBottomRight;
print $p->y, ' ', $p->x, "\n";
__END__
0 0
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