Here is one way that appears to fulfill your requirements.

use Win32::Process;

my $user = $ENV{USERNAME};
my $message    = "$0 has a message for $user";
send_message($message);

sub send_message
{
    my ($message) = @_;
    my $Process;
    my $program = 'C:/WINNT/system32/net.exe';
    Win32::Process::Create($Process, 
    "$program",
    "net send $user $message", 
    0, 
    DETACHED_PROCESS, 
    ".") or die "Create: $!";    
}
[download]

--
Regards,
Helgi Briem
helgi AT decode DOT is