to PG-CONNECT may designate the directory containing the local
   PostgreSQL unix socket (often "/var/run/postgresql/"). The HOST
   argument is assumed to designate a local directory rather than a
   hostname when its first character is #\/. You may need to modify
   authentication options in the PostgreSQL configuration file
   pg_hba.conf to allow connections over a unix-domain socket where
   the databse username is not equal to your ident tokens. This is an
   incompatible change to previous support for unix-domain sockets
   with CMUCL (previously a HOST of NIL told pg-dot-lisp to connect
   to a unix-domain socket whose name was hardwired into the library).
   This support currently exists for SBCL, CMUCL and OpenMCL.