Thank you for the help.
All of those examples worked perfectly.
And I've bookmarked the API reference... it is definately my friend. The MOB browser isn't enough to go on.
Using the reference I got the permissions to update:
my $currentPermission = $authorizationMgr->RetrieveEntityPermissions(entity => $service_content->rootFolder, inherited => 'false') ;
my $addPermission = Permission->new( group => '0', principal => $add_user, propagate => '1', roleId => $add_roleId);
push (@$currentPermission, $addPermission);
$authorizationMgr->SetEntityPermissions( entity => $service_content->rootFolder, permission => $currentPermission);
So thanks again and by the way your blog and other scripts were create places to look at examples.