my $res = $dbh->selectall_arrayref(<<'SQL');
 SELECT id, title FROM tbl_articles
 SQL

 my @subs = (
    [
        'Using string subst' => sub {
            for (@$res) {
                $dbh->do(
                'UPDATE tbl_articles SET title = '.
                $dbh->quote('##'.$_->[1])." WHERE id = $_->[0]");
            }
        },
    ],
    [
        'Using placeholders' => sub {
            my $sth = $dbh->prepare(<<'SQL');
 UPDATE tbl_articles SET title = ? WHERE id = ?
 SQL
            for (@$res) {
                $sth->execute(@{$_}[1,0]);
            }
        },
    ],
 );

 for (@subs) {
    print "$_->[0]:\n";
    timethis(100, $_->[1]);
 }

##</code><code>##

 Using string subst:
 timethis 100: 15 wallclock secs ( 2.33 usr +  0.78 sys =  3.11 CPU)
 Using placeholders:
 timethis 100: 15 wallclock secs ( 2.45 usr +  0.97 sys =  3.42 CPU)