HTML:
<a href="../cgi-bin/listusers.pl?alpha=ABC">ABC</a>
<a href="../cgi-bin/listusers.pl?alpha=DEF">DEF</a>
etc....

##</code><code>##

my $alpha = $query->param('alpha');

$alpha =~ /(\w)(\w)(\w)/;
$stmt = "SELECT * FROM teamnew ORDER BY lastname WHERE lastname REGEXP '^$1|^$2|^$3'";

##</code><code>##

"SELECT * FROM teamnew ORDER BY lastname WHERE lastname REGEXP '^A|^B|^C'"