It would appear that MySQL has native support for this, albeit in a non-standard way. I know that Oracle does as well through the MERGE statement. A more standard-respecting way to do it would be to try the update first and then, if the update returns no rows, try the insert, ie.

my $rowcount = $update_stm->execute(@args);
if ($rowcount == 0) {
    $insert_stm->execute(@other_args);
}
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