Access to the database itself from your Perl function can be done via
   an experimental module DBD::PgSPI
   (also available at CPAN
   mirror sites). This module makes available a
   DBI-compliant database-handle named
   $pg_dbh that can be used to perform queries
   with normal DBI syntax.
  
PL/Perl itself presently provides only one additional Perl command:
elog level, msgEmit a log or error message. Possible levels are DEBUG, LOG, INFO, NOTICE, WARNING, and ERROR. ERROR raises an error condition: further execution of the function is abandoned, and the current transaction is aborted.