PostgreSQL and DBI/DBD...vs Pg.pm

I'm getting confused between the methods of connectivity with PERL.
Right now I'm accessing several MySQL tables using DBI/DBD. However,
I'd like to convert these programs into PostgreSQL apps.  So, I'm
assuming that since I used DBI (a common database connection format)
that I'd only have to change the connect string to point to the
PostgreSQL source rather than MySQL and all should be good.

So, what is Pg.pm? and how is that connected (if at all) to DBI?
I'm running 6.3 on Redhat 5, and psql seems to work Ok.  I look in the
src/interfaces/perl5/ and All I see are files for Pg...and nothing
mentions DBI.  Then, I search Altavista and come up with this in the
latest from CPAN under DBI:

http://www.perl.com/CPAN-local/modules/by-category/07_Database_Interfaces/DB
D/DBD-Pg-0.68.readme

Ok, so the source for PG.pm is version 1.7.0 or so, and the version of this
DBD-Pg is 0.68.  Do these numbers have ANYTHING to do with each other,
or are they two separate products?  Which one do I need, and if I need
the DBD from CPAN (as I suspect), will it work with 6.3?

Dante

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