pg_connect works, DBI::connect says permission denied

Hello,
  I'm having problems connecting to my Postgres database using DBI::connect in Perl.

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DBI connect('dbname=visualizer','visualizer',...) failed: could not connect to server: Permission denied
       Is the server running locally and accepting
       connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
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Two important things to note:
  1)  The permissions on both the /tmp directory and the socket file are 777 (full access)
  2)  I can connect to the same database just fine using pg_connect in PHP

I just installed everything on a new server, and everything worked fine on the old one.
I figure I missed some configuration detail somewhere.  Any ideas?

Here are the versions I'm using:
  PostgreSQL 7.4.8
  PHP 4.3.9
  Perl 5.8.5
  Don't remember which version of Redhat I have

Thanks in advance for your consideration,
   RYan Miller