#! perl -slw
use strict;
use Win32::API::Prototype;;

{
    local $^W = 0; ## Ignore warning from Win32::API::Prototype
    ApiLink( 'kernel32', 'HANDLE GetCurrentProcess( )' ) or die $^E;
    ApiLink( 'kernel32', 'HRESULT SetPriorityClass( HANDLE p, DWORD c )' )
        or die $^E;
}

SetPriorityClass( GetCurrentProcess(), -1 );
print "Check priority for process $$ in the Task Manager";
## You should see that it has been set to 'LOW'
<STDIN>;