sub my_request {
    my($session_id, $data) = @_;
    eval {
        <insert $session_id, $data into table>
    };
    if($@) {
        if($@ ne primary_key_violation) {
            <Handle error>
        } # No else, since the primary_key_violation
          # just means that the data has been inserted
          # by another request
     }
     <Print everything is okay>
}