my $sql1 = <<SQL_END;
insert into t ( tstamp,            message )
       values ( current_timestamp, ?       )
SQL_END

##</code><code>##

  $db->do( 'insert into t values ( current_timestamp, '
    . $db->quote( $var1 )
    . ' )'
  ) or die "SQL go boom " . $db->errstr;

##</code><code>##

my $sth = $db->prepare( $sql1 ) or die(...);
...
$sth->execute( $var );