A few comments

I would change "getOracleRowHahs" to

sub getOracleRowHash{
    
    my $odbh = shift; 
    my $osth = $odbh->prepare("select pk from emp");
    $osth->execute();
    
    my $tableref;
    while(my $row = $osth->fetchrow_hashref()){
        no warnings;
        $tableref->{$row->{'pk'}} = $row;
}
    return $tableref;
}
[download]

and the call to

my $oracleTableHash = getOracleRowHash($odbh);
[download]

No need to connect twice and the use of the & is no longer suggested. Just request the one var since that is all you want now. Changing it to a array fetch may speed it up significantly, but that is left as a exercise. Also note the case change to follow your table definition.

In the while(my @row = $ssth->fetchrow_array()){ loop you re-prepare your insert every time. That is going to cost you. Also after a DBA changed the native variable order on me i always include variable names for all but the most trivial tasks.

my @vnames=qw/ 
 pk
    File_name 
    Cl_file_size_in_bytes
    Cl_checksum
    CL_created_date_time
    Status 
    Mn_file_size_in_bytes
    Mn_checksum 
    Failed_retries 
    Processed_date_time
    ftp_acknowledgement
    ohf_processing_status 
    ohf_processing_datetime
    ohf_total_rows
    ohf_failed_rows 
    ohf_processed_rows 
    hdfs_processing_status
    hdfs_processing_datetime 
    hdfs_checksum
    hdfs_file_size_in_bytes
/; 
    my $vlist=join(',',@vnames); 
    my $table='cloverleaf_ingestion'; 

    my @qs=map{'?'} @vnames; 
    my $q=join(',',@q); 

    my $query = "select $vlist from $table";
    my $ssth = $sdbh->prepare($query)    ||    die "Error in prepare t
+o mysql: $DBI::errstr\n";;
    my $insertquery = "insert into $table($vnames) values($q)";
    my $osth = $odbh->prepare($insertquery) || die "Error in prepare: 
+$DBI::errstr";
    $osth->begin_work; 

    $ssth->execute()    ||    die "Error in execute to mysql: $DBI::er
+rstr\n";;
    my $commit_ct      =500; 
    my $inserts=0; 

    while(my @row = $ssth->fetchrow_array()){
        if(!(exists($oracleTableHash->{$row[0]}))){
            $inserts++; 
            if ($inserts>$commit_ct){ 
                $inserts=1;
                $osth->commit or die 'something'; 
                $osth->begin_work; 
            }   
            $osth->execute(@row);
        }
    }
    $osth->commit or die 'something';
[download]

Note too the begin_work/commit calls that will speed up the insert a WHOLE BUNCH!!! The commit_ct test is to limit the size of the internal "holding" list that begin_work creates;