my %sth;
foreach( qw( guest name shoe_size ) ) {
  $sth{$_} = $dbh->prepare( qq{
SELECT distinct email from contacts where $_ = ? order by email
}) or warn "Error preparing for $_: " . $dbh->errstr . "\n";
}

##</code><code>##

$sth{$column} ||= $dbh->prepare( make_select( $column ) );