There seems to be no method for creating a Win32::Process object from a pid.

Actually there is:

Win32::Process::Open( $obj, $pid, $iflags );
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$pid is an existingprocess id as return by open2(), $obj is a variable you pass in which gets set to a Win32::Process object handle. You can the call ->SetPriority() on that. Eg.

use Win32::Process;;

$pid = system 1, 'notepad';; ## The return from open2 should work just
+ as well.

Win32::Process::Open( $o, $pid, 0 );;

print $o;;
Win32::Process=SCALAR(0x4073208)

$o->SetPriorityClass( IDLE_PRIORITY_CLASS );;
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