Shell Script Programming -- Loading data into table

Question

Hello Gurus
I am using Oracle's sql*loader utility to load data into a table. Lately, I got an unlikely scenario where in I need to process the data file first before loading it into the table and where I need help from you guys.
Consider the following data line
"Emp", DOB, Gender, Subject
"1",01/01/1980,"M","Physics:01/05/2010"
"2",01/01/1981,"M","Chemistry:02/05/2010|Maths:02/06/2011"
"3",01/01/1982,"M","Maths:03/05/2010|Physics:06/07/2010|Chemistry:08/09/2011"
"4",01/01/1983,"M","Biology:09/09/2010|English:10/10/2010"Employee - 1 will get loaded as a single record in the table. But I need to put Subject value into two separate fields into table. i.e. Physics into one column and date - 01/05/2010 into separate column.
Here big problem starts
Employee - 2 Should get loaded as 2 records into the table. The first record should have Chemistry as subject and date as 02/05/2010 and the next record should have all other fields same except the subject should be Maths and date as 02/06/2011. The subjects are separated by a pipe "|" in the data file.
Similarly, Employee 3 should get loaded as 3 records. One as Maths, second as Physics and third as Chemistry along with their respective dates.
I hope I have made my problem clear to everyone.
I am looking to do something in shell scripting such that before finally running the sql*loader script, the above 4 employees have their records repeated as many times as their subject changes.
In summary 2 problems are described above.
1. To load subject and date into 2 separate fields in Oracle table at the time of load.
2. If their exists multiple subjects then a record is to be loaded that many times as there exists any changes in employee's subject.
Any help would be much appreciated.
Thanks.

Answer 1

Here are some comments. Perl can be a little cryptic but once you get used to it, it can be pretty powerful.
#!/usr/bin/perl -w
my $line_count = 0;
open FILE, "test_file" or die $!;
# Read each line from the file.
while (my $line = <FILE>) {
    # Print the header if it is the first line.
    if ($line_count == 0) {
        chomp($line);
        print $line . ", Date\n";
        ++$line_count;
        next;   
    # Get all the columns (as separated by ',' into an array)
    my @columns = split(',', $line);
    # Remove the newline from the fourth column.
    chomp($columns[3]); 
    # Read the fields (separated by pipe) from the fourth column into an array.
    my @subject_and_date = split('\|', $columns[3]);     
    # Loop for each subject and date.
    foreach my $sub_and_date (@subject_and_date) {
        # Print value of Emp, DOB, and Gender first.
        print $columns[0] . "," . $columns[1] . "," . $columns[2] . ",";
        # Remove all double quotes from the subject and date string.
        $sub_and_date =~ s/"//g;
        # Replace ':' with '","'
        $sub_and_date =~ s/:/","/;
        print '"' . $sub_and_date . '"' . "\n";       
    ++$line_count;
close FILE;