ActivePerlからSQLiteのDBへアクセスする

うーん。これで動くはずなんだけど、InternalServerエラーになる（ ´Д⊂ヽ
会社で調べよう‥‥

#!C:/perl/bin/perl
#use strict;

use DBI;
my $db = 'mydb.db';
my $dbh = DBI->connect("dbi:SQLite:dbname=$db", '', '');

my $sth = $dbh->prepare('SELECT * FROM sample');

$sth->execute;
my @row = $sth->fetchrow_array();
print "Content-Type: text/html\n\n";

print "\n";
print <<"END"

$row[1]


$row[2]


END
$sth->finish();

$dbh->disconnect();

DBD::SQLite::db prepare failed: file is encrypted or is not a database(26) at db

dimp.c line 269 at db.cgi line 9.

Can't call method "execute" on an undefined value at db.cgi line 10.

という表示が出るんだが、prepareで失敗してるらしい。DBが認識できてない？