my $LIMIT = 30;

my $sth = $dbh->prepare("SELECT foo, bar FROM table WHERE baz=?");
$sth->execute( $baz );

my ( @rows, @row );
for ( 1 .. $LIMIT ) {
    last unless ( @row = $sth->fetchrow_array );
    push @rows, [ @row ];
}

#do stuff with @rows