Here is the line that is exiting your script:

die qq(SQL fail "$rc":), $db->Error(),qq(n) if $rc;

Just handle the error differently. Check $rc or $db->Error(), and continue with the next insert if the error points to a duplicate value.

# untested
if ($rc == WHATEVER_ERROR_IS_GENERATED_BY_DUPLICATE) {
    # you can also test ($db->Error() =~ /some value/)
    next;
} else {
    die qq(SQL fail "$rc":), $db->Error(),qq(n);
}
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Your script will still die if the insert fails for a different reason.

HTH...