Hi,
In my experience, writing a program to stay open and monitor a directory is easier: you readdir the contents, sleep, and readdir again, comparing the arrays and firing off a sub to process the new files. Create a hash and get the mtimes from stat if you want to check if files inside the dir have been changed.
If you wanted to write a script that ended and needed to be restarted by crond you could look at Storable.

As far as talking to Oracle - it's easy enough; perldoc DBD::Oracle should tell you what you need to know. It's not much different than talking to any other DB.

$dbh = DBI->connect("dbi:Oracle:host=$orasrvr;sid=$sid", "$uname","$pa
+ss");
[download]

should get you started.

Loaders can be as simple or complicated as the business logic dictates. You process each line and decide what to do with it. I've had to pull a table from a db into a hash and check if each line of a file existed in the hash, and I've had simple tasks like building a SQL INSERT query aroud data in each line.