if ($po->status->name eq 'Pending') {
    # po can be sent
}

# later

if ($po->status->name eq 'Pending' || $po->status->name eq 'Sent') {
    # po can be cancelled
}

##</code><code>##

if ($po->can_send) {
    # po can be sent
}

# later

if ($po->can_cancel) {
    # po can be cancelled
}