Your pseudocode above suffers from a problem: in creating your database handle, you set RaiseError to true. This means that your script will die on any database error, which is exactly what you don't want. At a bare minimum, you would likely want something closer to:

my $dbh = DBI->connect("DBI:mysql:database=$sql_database;host=$sql_hos
+t;port=$sql_port",
                       $username,
                       $password,
                       {
                            RaiseError => 0,
                        }
                       )
    or die "DB connect failed: $DBI::errstr";
    
for my $record (@records) {
    unless ($dbh->do($insertstr,
                     undef,
                     $slice->seq_region_name(),
                     $vf->start $vf->variation_name(),
                     $vf->allele_string()
            )) {
        print INSERTLOG "failed to insert", , "\n";

    } #end unless
}#end loop
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However, if you are doing multiple inserts, I would suggest preparing a single statement outside the loop and then binding parameters and executing inside the loop. You'll also likely want to use $DBI::errstr to output more useful diagnostics. This is all discussed in DBI. See RaiseError, Placeholders_and_Bind_Values, $DBI::errstr, and PrintError.