Stored Procedure: PL/Perl or PL/SQL?

Greetings all,

I'm working to integrate an accounting system
(http://www.linuxcanada.com) with another application.  Fortunately,
both use PG, so integration should be easy.

I want to be able to insert invoices, and invoice line items, into the
accounting system.  As you might expect, this requires many selects and
inserts involving serveral tables wrapped around a transaction.  As I
see it, there are a couple of ways to do this:

1. Attach a trigger which runs a Stored Procedure in PL/SQL;

2. Create a Perl Module that connects to a database via DBI and does the
work; the trigger would then be written in PL/Perl, and would use the
Perl Module to do the work.

The advantage to #2 is that I'd have invoice migration and a
general-purpose module for inserting invoices, with the same amount of
work that I'd have for just invoice migration using PL/SQL.  The
drawback is the overhead of using Perl inside PG; how much overhead is
there?

What else should I consider?

Thanks,
-Josh