IMHO it might be even better to forbid mysql to do that insert at all. if you turn to strict mode, the insert will fail and output a warning. with the "RaiseError" option on, it will die:

my $dbh = DBI->connect(..., { RaiseError => 1 });
$dbh->do(q{SET sql_mode="STRICT_TRANS_TABLES,STRICT_ALL_TABLES"});
# insert
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Then you can be sure to not get wrong data inserted, but you have to put an eval block around it to catch the error.