&main::execute undefined?

Ok, I'm running Postgres and RH8 right out-of-the-box.  DBD::Pg is installed, and I'm using Perl 5.8 -- all right out-of-the-box.  When my script gets to this line:

$statementH = execute() || die $statementH->errstr ;  # this is line 10 btw

I get:

Undefined subroutine &main::execute called at ./test.pl line 10.

As far as I can tell, it should work --but doesn't so I must be missing something.  If you want to tackle this one, everything is right below:  (PS:  the query going into $sql I got with help of you all, so thanks!)

========

#! /usr/bin/perl -w

use DBI ;

$dbH = (DBI->connect("DBI:Pg:dbname=lanparty-reservations","andrew","shrp1234")) ;
$sql = "select c.relname as table from pg_class c where c.relkind = 'r' and c.relname !~ '^pga_' and c.relname !~ '^pg_'" ;

$statementH = $dbH->prepare($sql) ;
$statementH = execute() || warn $statementH->errstr ;