Here is a bit that uses PPM::Installer to .. well.. install..

use strict;
use PPM::UI;

my $target_list = PPM::UI::target_list();
my $rep_list = PPM::UI::repository_list();

PPM::UI::install( $rep_list->{ "result" }, $target_list->result->[0], 
+"XML::Tiny", {"dryrun" => 0}, \&status_callback));


sub status_callback
{
     my($name, $version,   $tname, $something, $p0, $p1, $p2) = @_;

     print "$name \t $version \t $tname \t $something \t $p0 \t $p1 \t
+ $p2 \n";
}
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There are some $opts for the install call - "from", "force", "follow" and "dryrun". The first 3 are as-is from PPM3.bat. "dryrun" is just what it says - show you what its going to do without actually doing it.